Animal models and therapeutic molecules

ABSTRACT

The invention discloses methods for the generation of chimaeric human—non-human antibodies and chimaeric antibody chains, antibodies and antibody chains so produced, and derivatives thereof including fully humanised antibodies; compositions comprising the antibodies, antibody chains and derivatives, as well as cells, non-human mammals and vectors, suitable for use in the methods.

CROSS REFERENCE

This application is a continuation of U.S. application Ser. No.15/690,183 filed Aug. 29, 2017, which is a continuation of U.S.application Ser. No. 13/846,672 filed Mar. 18, 2013, the contents ofeach are herein incorporated by reference in their entirety.

BACKGROUND

The present invention relates inter alia to non-human animals and cellsthat are engineered to contain exogenous DNA, such as humanimmunoglobulin gene DNA, their use in medicine and the study of disease,methods for production of non-human animals and cells, and antibodiesand antibody chains produced by such animals and derivatives thereof.

In order to get around the problems of humanizing antibodies a number ofcompanies set out to generate mice with human immune systems. Thestrategy used was to knockout the heavy and light chain loci in ES cellsand complement these genetic lesions with transgenes designed to expressthe human heavy and light chain genes. Although fully human antibodiescould be generated, these models have several major limitations:

(i) The size of the heavy and light chain loci (each several Mb) made itimpossible to introduce the entire loci into these models. As a resultthe transgenic lines recovered had a very limited repertoire ofV-regions, most of the constant regions were missing and importantdistant enhancer regions were not included in the transgenes.

(ii) The very low efficiency of generating the large insert transgeniclines and the complexity and time required to cross each of these intothe heavy and light chain knockout strains and make them homozygousagain, restricted the number of transgenic lines which could be analysedfor optimal expression.

(iii) Individual antibody affinities rarely reached those which could beobtained from intact (non-transgenic) animals.

WO2007117410 discloses chimaeric constructs for expressing chimaericantibodies.

WO2010039900 discloses knock in cells and mammals having a genomeencoding chimaeric antibodies.

The present invention provides, inter alia, a process for the generationin non-human mammals of antibodies that comprise a human Ig variableregion, and further provides non-human animal models for the generationof such antibodies.

SUMMARY OF THE INVENTION

All nucleotide co-ordinates for the mouse are those corresponding toNCBI m37 for the mouse C57BL/6J strain, e.g. April 2007 ENSEMBL Release55.37h, e.g. NCBI37 July 2007 (NCBI build 37) (e.g. UCSC version mm9 seeWorld Wide Web (www) genome.ucsc.edu and World Wide Web (www)genome.ucsc.edu/FAQ/FAQreleases.html) unless otherwise specified. Humannucleotides coordinates are those corresponding to GRCh37 (e.g. UCSCversion hg 19, World Wide Web (www)genome.ucsc.edu/FAQ/FAQreleases.html), February 2009 ENSEMBL Release55.37, or are those corresponding to NCBI36, Ensemble release 54 unlessotherwise specified. Rat nucleotides are those corresponding to RGSC 3.4Dec. 2004 ENSEMBL release 55.34w, or Baylor College of Medicine HGSCv3.4 Nov. 2004 (e.g., UCSC rn4, see World Wide Web (www) genome.ucsc.eduand World Wide Web (www) genome.ucsc.edu/FAQ/FAQreleases.html) unlessotherwise specified.

In the present invention, methods are disclosed for constructing achimaeric human heavy and light chain loci in a non-human mammal, forexample a mouse. Reference to work in mice herein is by way of exampleonly, and reference to mice is taken to include reference to allnon-human mammals unless otherwise apparent from the disclosure, withmice being preferred as the non-human mammal.

In one aspect the invention relates to a non-human mammal whose genomecomprises:

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region; and    -   (b) optionally one or more human Ig light chain kappa V regions        and one or more human Ig light chain kappa J regions upstream of        the host non-human mammal kappa constant region and/or one or        more human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region;        wherein the non-human mammal is able to produce a repertoire of        chimaeric antibodies, or chimaeric light or heavy chains, having        a non-human mammal constant region and a human variable region.

In one aspect the invention relates to non-human mammal whose genomecomprises

-   -   (a) a plurality of human Ig light chain kappa V regions and one        or more human Ig light chain kappa J regions upstream of the        host non-human mammal kappa constant region and/or a plurality        of human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region; and    -   (b) optionally one or more human IgH V regions, one or more        human D regions and one or more human J regions upstream of the        host non-human mammal constant region;        wherein the non-human mammal is able to produce a repertoire of        chimaeric antibodies, or chimaeric light or heavy chains, having        a non-human mammal constant region and a human variable region.

In one aspect the invention relates to non-human mammalian cell whosegenome comprises

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region and    -   (b) optionally one or more human Ig light chain kappa V regions        and one or more human Ig light chain kappa J regions upstream of        the host non-human mammal kappa constant region and/or one or        more human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region.

In one aspect the invention relates to a non-human mammalian cell whosegenome comprises

-   -   (a) a plurality of human Ig light chain kappa V regions and one        or more human Ig light chain kappa J regions upstream of the        host non-human mammal kappa constant region and/or a plurality        of human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region; and    -   (b) optionally one or more human IgH V regions, one or more        human D regions and one or more human J regions upstream of the        host non-human mammal constant region;

In a further aspect the invention relates to a method for producing anon-human cell or mammal comprising inserting into a non-human mammalcell genome, such as an ES cell genome;

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region; and    -   (b) optionally one or more human Ig light chain kappa V regions        and one or more human Ig light chain kappa J regions upstream of        the host non-human mammal kappa constant region and/or one or        more human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region; respectively, the insertion being        such that the non-human cell or mammal is able to produce a        repertoire of chimaeric antibodies having a non-human mammal        constant region and a human variable region, wherein steps (a)        and (b) can be carried out in either order and each of steps (a)        and (b) can be carried out in a stepwise manner or as a single        step. Insertion may be by homologous recombination.

In a further aspect the invention relates to a method for producing anantibody or antibody chain specific to a desired antigen the methodcomprising immunizing a transgenic non-human mammal as disclosed hereinwith the desired antigen and recovering the antibody or antibody chain.

In a further aspect the invention relates to a method for producing afully humanised antibody comprising immunizing a transgenic non-humanmammal as disclosed herein with the desired antigen, recovering theantibody or cells producing the antibody and then replacing thenon-human mammal constant region with a human constant region, forexample by protein or DNA engineering.

In a further aspect the invention relates to humanised antibodies andantibody chains produced according to the present invention, both inchimaeric (for example, mouse-human) and fully humanised form, as wellas fragments and derivatives of said antibodies and chains, and use ofsaid antibodies, chains and fragments in medicine, including diagnosis.

In a further aspect the invention relates to use of a non-human mammalas described herein as a model for the testing of drugs and vaccines.

In one aspect the invention relates to a non-human mammal whose genomecomprises:

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region; and    -   (b) optionally one or more human Ig light chain kappa V regions        and one or more human Ig light chain kappa J regions upstream of        the host non-human mammal kappa constant region and/or one or        more human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region;        wherein the non-human mammal is able to produce a repertoire of        chimaeric antibodies or antibody chains having a non-human        mammal constant region and a human variable region.

In a further aspect the invention relates to a non-human mammal whosegenome comprises:

-   -   (a) a plurality of human Ig light chain kappa V regions and one        or more human Ig light chain kappa J regions upstream of the        host non-human mammal kappa constant region and/or a plurality        of human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region; and    -   (b) optionally one or more human IgH V regions, one or more        human D regions and one or more human J regions upstream of the        host non-human mammal constant;        wherein the non-human mammal is able to produce a repertoire of        chimaeric antibodies having a non-human mammal constant region        and a human variable region.

Optionally the non-human mammal genome is modified to prevent expressionof fully host-species specific antibodies.

In one aspect the inserted human DNA comprises at least 50% of the humanheavy chain variable (V) genes, such as at least 60%, at least 70%, atleast 80%, at least 90%, and in one aspect all of the human V genes.

In one aspect the inserted human DNA comprises at least 50% of the humanheavy chain diversity (D) genes, such as at least 60%, at least 70%, atleast 80%, at least 90%, and in one aspect all of the human D genes.

In one aspect the inserted human DNA comprises at least 50% of the humanheavy chain joining (J) genes, such as at least 60%, at least 70%, atleast 80%, at least 90%, and in one aspect all of the human J genes.

In one aspect the inserted human DNA comprises at least 50% of the humanlight chain Variable (V) genes, such as at least 60%, at least 70%, atleast 80%, at least 90%, and in one aspect all of the human light chainV genes.

In one aspect the inserted human DNA comprises at least 50% of the humanlight chain joining (J) genes, such as at least 60%, at least 70%, atleast 80%, at least 90%, and in one aspect all of the human light chainJ genes.

The inserted human genes may be derived from the same individual ordifferent individuals, or be synthetic or represent human consensussequences.

Although the number of V D and J regions is variable between humanindividuals, in one aspect there are considered to be 51 human V genes,27 D and 6 J genes on the heavy chain, 40 human V genes and 5 J genes onthe kappa light chain and 29 human V genes and 4 J genes on the lambdalight chain (Janeway and Travers, Immunobiology, Third edition)

In one aspect the human heavy chain locus inserted into the non-humanmammal contains the full repertoire of human V, D and J regions, whichin the genome is in functional arrangement with the non-human mammalconstant regions such that functional chimaeric antibodies can beproduced between the human variable and non-human mammal constantregions. This total inserted human heavy chain genetic material isreferred to herein as the human IgH VDJ region, and comprises DNA from ahuman genome that encodes all the exons encoding human V, D and Jportions and suitably also the associated introns. Similarly, referenceto the human Ig light chain kappa V and J regions herein refers to humanDNA comprising all the exons encoding V and J regions and suitably alsothe associated introns of the human genome. Reference to the human Iglight chain lambda V and J regions herein refers to human DNA comprisingall the exons encoding V and J regions and suitably also the associatedintrons of the human genome.

Human variable regions are suitably inserted upstream of a non-humanmammal constant region, the latter comprising all of the DNA required toencode the full constant region or a sufficient portion of the constantregion to allow the formation of an effective chimaeric antibody capableof specifically recognising an antigen.

In one aspect the chimaeric antibodies or antibody chains have a part ofa host constant region sufficient to provide one or more effectorfunctions seen in antibodies occurring naturally in a host mammal, forexample that they are able interact with Fc receptors, and/or bind tocomplement.

Reference to a chimaeric antibody or antibody chain having a host nonmammal constant region herein therefore is not limited to the completeconstant region but also includes chimaeric antibodies or chains whichhave all of the host constant region, or a part thereof sufficient toprovide one or more effector functions. This also applies to non-humanmammals and cells and methods of the invention in which human variableregion DNA may be inserted into the host genome such that it forms achimaeric antibody chain with all or part of a host constant region. Inone aspect the whole of a host constant region is operably linked tohuman variable region DNA.

The host non-human mammal constant region herein is preferably theendogenous host wild-type constant region located at the wild typelocus, as appropriate for the heavy or light chain. For example, thehuman heavy chain DNA is suitably inserted on mouse chromosome 12,suitably adjacent the mouse heavy chain constant region.

In one aspect the insertion of the human DNA, such as the human VDJregion is targeted to the region between the J4 exon and the Cμ locus inthe mouse genome IgH locus, and in one aspect is inserted betweenco-ordinates 114,667,090 and 114,665,190, or at coordinate 114,667,091,after 114,667,090. In one aspect the insertion of the human DNA, such asthe human light chain kappa VJ is targeted into mouse chromosome 6between co-ordinates 70,673,899 and 70,675,515, suitably at position70,674,734, or an equivalent position in the lambda mouse locus onchromosome 16.

In one aspect the host non-human mammal constant region for forming thechimaeric antibody may be at a different (non endogenous) chromosomallocus. In this case the inserted human DNA, such as the human variableVDJ or VJ region(s) may then be inserted into the non-human genome at asite which is distinct from that of the naturally occurring heavy orlight constant region. The native constant region may be inserted intothe genome, or duplicated within the genome, at a different chromosomallocus to the native position, such that it is in a functionalarrangement with the human variable region such that chimaericantibodies of the invention can still be produced.

In one aspect the human DNA is inserted at the endogenous host wild-typeconstant region located at the wild type locus between the host constantregion and the host VDJ region.

Reference to location of the variable region upstream of the non-humanmammal constant region means that there is a suitable relative locationof the two antibody portions, variable and constant, to allow thevariable and constant regions to form a chimaeric antibody or antibodychain in vivo in the mammal. Thus, the inserted human DNA and hostconstant region are in functional arrangement with one another forantibody or antibody chain production.

In one aspect the inserted human DNA is capable of being expressed withdifferent host constant regions through isotype switching. In one aspectisotype switching does not require or involve trans switching. Insertionof the human variable region DNA on the same chromosome as the relevanthost constant region means that there is no need for trans-switching toproduce isotype switching.

As explained above, the transgenic loci used for the prior art modelswere of human origin, thus even in those cases when the transgenes wereable to complement the mouse locus so that the mice produced B-cellsproducing fully human antibodies, individual antibody affinities rarelyreached those which could be obtained from intact (non-transgenic)animals. The principal reason for this (in addition to repertoire andexpression levels described above) is the fact that the control elementsof the locus are human. Thus, the signalling components, for instance toactivate hyper-mutation and selection of high affinity antibodies arecompromised.

In contrast, in the present invention, host non-human mammal constantregions are maintained and it is preferred that at least one non-humanmammal enhancer or other control sequence, such as a switch region, ismaintained in functional arrangement with the non-human mammal constantregion, such that the effect of the enhancer or other control sequence,as seen in the host mammal, is exerted in whole or in part in thetransgenic animal.

This approach above is designed to allow the full diversity of the humanlocus to be sampled, to allow the same high expression levels that wouldbe achieved by non-human mammal control sequences such as enhancers, andis such that signalling in the B-cell, for example isotype switchingusing switch recombination sites, would still use non-human mammalsequences.

A mammal having such a genome would produce chimaeric antibodies withhuman variable and non-human mammal constant regions, but these could bereadily humanized, for example in a cloning step. Moreover the in vivoefficacy of these chimaeric antibodies could be assessed in these sameanimals.

In one aspect the inserted human IgH VDJ region comprises, in germlineconfiguration, all of the V, D and J regions and intervening sequencesfrom a human.

In one aspect 800-1000 kb of the human IgH VDJ region is inserted intothe non-human mammal IgH locus, and in one aspect a 940, 950 or 960 kbfragment is inserted. Suitably this includes bases 105,400,051 to106,368,585 from human chromosome 14.

In one aspect the inserted IgH human fragment consists of bases105,400,051 to 106,368,585 from chromosome 14. In one aspect theinserted human heavy chain DNA, such as DNA consisting of bases105,400,051 to 106,368,585 from chromosome 14, is inserted into mousechromosome 12 between the end of the mouse J4 region and the Eμ region,suitably between co-ordinates 114,667,090 and 114,665,190, or atco-ordinate 114,667,091, after 114,667,090. In one aspect the insertionis between co-ordinates 114,667,089 and 114,667,090 (co-ordinates referto NCBI m37, for the mouse C57BL/6J strain), or at equivalent positionin another non-human mammal genome.

In one aspect the inserted human kappa VJ region comprises, in germlineconfiguration, all of the V and J regions and intervening sequences froma human. Suitably this includes bases 88,940,356 to 89,857,000 fromhuman chromosome 2, suitably approximately 917 kb. In a further aspectthe light chain VJ insert may comprise only the proximal clusters of Vsegments and J segments. Such an insert would be of approximately 473kb. In one aspect the human light chain kappa DNA, such as the human IgKfragment of bases 88,940,356 to 89,857,000 from human chromosome 2, issuitably inserted into mouse chromosome 6 between co-ordinates70,673,899 and 70,675,515, suitably at position 70,674,734. Theseco-ordinates refer to NCBI36 for the human genome, ENSEMBL Release 54and NCBIM37 for the mouse genome, relating to mouse strain C57BL/6J.

In one aspect the human lambda VJ region comprises, in germlineconfiguration, all of the V and J regions and intervening sequences froma human.

Suitably this includes analogous bases to those selected for the kappafragment, from human chromosome 2.

A cell or non-human mammal of the invention, in one embodiment,comprises an insertion of human heavy chain variable region DNA betweenco-ordinates 114, 666, 183 and 114, 666, 725, such as between 114 666283 and 114 666 625, optionally between co-ordinates 114,666,335 and114,666,536, optionally between 114,666,385 and 114,666,486, or between114,666,425 and 114,666,446, or between 114,666,435 and 114,666,436 ofmouse chromosome 12 with reference to NCBIM37 for the mouse genome,relating to mouse strain C57BL/6J or an equivalent position of mousechromosome 12 from a different mouse strain or an equivalent position inthe genome of another non-human vertebrate, e.g., a rat. The insertionbetween co-ordinates 114,666,435 and 114,666,436 relating to mousestrain C57BL/6J is equivalent to an insertion between co-ordinates1207826 and 1207827 on chromosome 12 with reference to the 129/SvJgenomic sequence of the GenBank® access number NT114985.2. An insertionmay be made at equivalent position in another genome, such as anothermouse genome. In an example of this embodiment, the cell or mammal ofthe invention comprises a human IgH VDJ region which comprises orconsists of nucleotides 106,328,851-107,268,544, such as nucleotides106,328,901-107,268,494, such as nucleotides 106,328,941-107,268,454,such as nucleotides 106,328,951-107,268,444 of human Chromosome 14, withreference to the GRCH37/hg19 sequence database, or insertion ofequivalent nucleotides relating to chromosome 14 from a different humansequence or database. The human insertion may be made between theregions indicated above.

A cell or mammal of the invention, in one embodiment, comprises aninsertion of the human kappa VJ region, suitably comprising orconsisting of, in germline configuration, all of the V and J regions andintervening sequences from a human, the insertion of the human DNA beingmade between co-ordinates 70,673,918-70,675,517, such as betweenco-ordinates 70, 674,418 and 70 675, 017, such as between co-ordinates70,674, 655-70,674,856, such as between co-ordinates 70,674,705-70,674,906, such as between co-ordinates 70,674, 745-70,674,766,such as between co-ordinates 70,674,755 and 70,674,756 of mousechromosome 6, numbering with reference to NCBIM37 for the mouse genome,relating to mouse strain C57BL/6J, or an insertion at an equivalentposition in another genome, such as another mouse genome. In an exampleof this embodiment, a cell or mammal of the invention comprises aninsertion of nucleotides 89,159,079-89,630,437 and/or89,941,714-90,266,976 of human chromosome 2 with reference to theGRCH37/hg19 sequence database (or equivalent nucleotides relating tochromosome 2 from a different human sequence or database), such as aninsertion of these 2 discrete fragments without the interveningsequence, or an insertion of the complete 89,159,079-90,266,976 region.

The insertion may comprise, or consist, of:

-   -   (i) nucleotides 89,158,979-89,630,537, such as        89,159,029-89,630,487, such as 89,159,069-89,630,447, such as        89,159,079-89,630,437, optionally in addition to fragment (ii)        below    -   (ii) nucleotides 89,941,614-90,267,076, such as        89,941,664-90,267,026, such as 89, 941,704-90,266,986, such as        89,941,714-90,266,976; optionally in addition to fragment (i)    -   (iii) nucleotides 89,158,979-90,267,076, such as nucleotides        89,159,079-90,266,976.

The human insertion may be made between the regions indicated above.

In an embodiment, a cell or mammal of the invention comprises aninsertion of a human lambda region which comprises at least one human Jλregion (eg, a germline region) and at least one human Cλ region (eg, agermline region), optionally C_(λ)6 and/or C_(λ)7. For example, the cellor mammal comprises a plurality of human Jλ regions, optionally two ormore of J_(λ)1, J_(λ)2, J_(λ)6 and J_(λ)7, optionally all of J_(λ)1,J_(λ)2, J_(λ)6 and J_(λ)7. In an example, the cell or mammal comprisesat least one human J_(λ)-C_(λ) cluster, optionally at leastJ_(λ)7-C_(λ)7.

In one aspect the human JC cluster is inserted 3′ of the last endogenousJ lambda or is inserted 3′ of the last endogenous J kappa region,suitably immediately 3′ of these sequences, or substantially immediately3′ of these sequences.

In one aspect the insertion into the mouse lambda locus is madedownstream of the endogenous C1 gene segment, for example where there isa 3′ J1C1 cluster, suitably immediately 3′ of the C1 segment, orsubstantially immediately 3′ of the segment.

In one aspect (e.g. cell or non-human mammal) a human JC cluster isinserted into a kappa locus and any resulting cell or animal isheterozygous at that locus, such that the cell has one chromosome withhuman lambda DNA inserted into the kappa locus, and another chromosomewith human kappa DNA at the endogenous kappa locus.

In an embodiment, a cell or mammal of the invention comprises a human Eλenhancer.

A cell or mammal may of the invention comprise an inserted human lambdaVJ region, suitably comprising or consisting of, in germlineconfiguration, all of the V and J regions and intervening sequences froma human, the inserted region comprises or consisting of nucleotides22,375,509-23,327,984, such as nucleotides 22,375,559-23,327,934, suchas nucleotides 22,375,599-23,327,894, such as nucleotides22,375,609-23,327,884 from human Chromosome 22, with reference to theGRCH37/hg19 sequence database, or equivalent DNA from another humansequence or database. The insertion into the mouse genome may be madebetween co-ordinates 19,027,763 and 19,061,845, such as betweenco-ordinates 19, 037, 763 and 19, 051, 845, such as between co-ordinates19,047,451 and 19,047,652, such as between co-ordinates 19,047,491 and19,047,602, such as between co-ordinates 19,047,541 and 19,047,562, suchas between co-ordinates 19,047,551 and 19,047,552 of mouse Chromosome 16(with reference to NCBIM37 for the mouse genome, relating to mousestrain C57BL/6J, equivalent to co-ordinates 1,293,646-1,293,647 of the129 SvJ genomic sequence in the sequence file of NT_039630.4), or may bean insertion at an equivalent position in other genome, such as anothermouse genome. The insertion of the human lambda nucleic acid into themouse genome may alternatively be made between co-ordinates 70,673,918and 70,675,517, such as between co-ordinates 70, 674,418 and 70 675,017, such as between co-ordinates 70,674,655 and 70,674,856, such asbetween co-ordinates 70,674,705 and 70,674,806, such as betweenco-ordinates 70,674,745 and 70,674,766, such as between co-ordinates70,674,755 and 70,674,756 of mouse Chromosome 6 (with reference toNCBIM37 for the mouse genome, relating to mouse strain C57BL/6J) orequivalent in another genome. The human insertion may be made betweenthe regions indicated above.

All specific human fragments described above may vary in length, and mayfor example be longer or shorter than defined as above, such as 500bases, 1 KB, 2K, 3K, 4K, 5 KB, 10 KB, 20 KB, 30 KB, 40 KB or 50 KB ormore, which suitably comprise all or part of the human V(D)J region,whilst preferably retaining the requirement for the final insert tocomprise human genetic material encoding the complete heavy chain regionand light chain region, as appropriate, as described above.

In one aspect the 5′ end of the human insert described above isincreased in length. Where the insert is generated in a stepwise fashionthen the increase in length is generally in respect of the upstream (5′)clone.

In one aspect the 3′ end of the last inserted human gene, generally thelast human J gene to be inserted is less than 2 kb, preferably less than1 KB from the human-mouse join region.

In one aspect the non-human mammal comprises some or all of the humanlight chain kappa VJ region as disclosed herein but not the human lightchain lambda VJ region.

In one aspect the cell or non-human mammal comprises a fully humanlambda locus (lambda VJC regions from a human), a chimaeric kappa locus(human kappa VJ regions operatively linked to a host kappa constantregion) and a chimaeric heavy chain locus, having a human VDJ regionoperatively linked to a host heavy chain constant region.

In a further aspect the genome comprises an insertion of V, D (heavychain only) and J genes as described herein at the heavy chain locus andone light chain locus, or at the heavy chain locus and both light chainloci. Preferably the genome is homozygous at one, or both, or all threeloci.

In another aspect the genome may be heterozygous at one or more of theloci, such as heterozygous for DNA encoding a chimaeric antibody chainand native (host cell) antibody chain. In one aspect the genome may beheterozygous for DNA capable of encoding 2 different antibody chains ofthe invention, for example, comprising 2 different chimaeric heavychains or 2 different chimaeric light chains.

In one aspect the invention relates to a non-human mammal or cell, andmethods for producing said mammal or cell, as described herein, whereinthe inserted human DNA, such as the human IgH VDJ region and/or lightchain V, J regions are found on only one allele and not both alleles inthe mammal or cell. In this aspect a mammal or cell has the potential toexpress both an endogenous host antibody heavy or light chain and achimaeric heavy or light chain.

In a further aspect of the invention the human VDJ region, or lightchain VJ region, is not used in its entirety, but parts of theequivalent human VDJ or VJ region, such as the exons, from other speciesmay be used, such as one or more V, D, or J exons from other species, orregulatory sequences from other species. In one aspect the sequencesused in place of the human sequences are not human or mouse. In oneaspect the sequences used may be from rodent, or, primate such as chimp.For example, 1, 2, 3, 4, or more, or all of the J regions from a primateother than a human may be used to replace, one, 2, 3, 4, or more or allof the human J exons in the VDJ/VJ region of the cells and animals ofthe invention.

In a further aspect the inserted human DNA, such as the human IgH VDJregion, and/or light chain VJ regions, may be inserted such that theyare operably linked in the genome with a mu constant region from anon-human, non-mouse species, such as a rodent or primate sequence, suchas a rat sequence.

Other non-human, non-mouse species from which DNA elements may be usedin the present invention include rabbits, lamas, dromedary, alpacas,camels and sharks.

In one aspect the inserted human DNA, such as the human VDJ or VJregion, is not operably linked to the endogenous host mu sequence butrather to a non-host mu sequence.

Operable linkage suitably allows production of an antibody heavy orlight chain comprising the human variable region.

In one aspect the inserted human DNA, such as the human IgH VDJ region(and/or light chain VJ regions) may be inserted into the host chromosometogether with mu constant region nucleic acid which is not host muconstant region nucleic acid, and preferably is a mu constant regionfrom a non-mouse, non-human species. Suitably the inserted human DNA,such as the human VDJ region (and/or light chain VJ regions) is operablylinked to a non-human, non-mouse mu, and is able to form a chimaericantibody heavy or light chain. In another aspect a non-mouse, non-humanmu may be inserted into the host chromosome on a separate geneticelement to that of the human variable region, or at a different locationin the genome, suitably operably linked to the variable region such thata chimaeric antibody heavy or light can be formed.

In an additional aspect the invention relates to a non-human mammal or acell whose genome comprises a plurality of human IgH V regions, one ormore human D regions and one or more human J regions upstream of a hostnon-human mammal light chain constant region, arranged such that thecell or mammal is able to express a chimaeric antibody chain. Theinvention also relates to a non-human mammal or a cell whose genomeadditionally or alternatively comprises a plurality of human Ig lightchain V regions, and one or more human J regions upstream of a hostnon-human mammal heavy chain constant region, such that the cell ormammal is able to express a chimaeric antibody chain. The cell or mammalmay be able to express an antibody having both heavy and light chains,including at least one chimaeric antibody chain, as disclosed above.

The inserted human heavy chain variable regions may be any of thosedescribed herein, and may be inserted at the positions described abovefor insertion 5′ of the lambda and kappa constant regions. Likewise theinserted human light chain variable regions may be those describedabove, and may be inserted at the positions described above forinsertion 5′ of the heavy chain constant region.

For example, the genome or the cell or non-human mammal of the inventionmay encode an antibody comprising an antibody chain having a human heavychain variable region upstream of a mouse light chain constant region,or an antibody chain having a human light chain variable region upstreamof a mouse heavy chain constant region, in combination with one of:

-   -   a fully human antibody light chain;    -   a fully human antibody heavy chain;    -   a non-human vertebrate (e.g., mouse or rat) antibody light        chain;    -   a non-human vertebrate (e.g., mouse or rat) antibody heavy        chain;    -   a chimaeric non-human vertebrate (e.g., mouse or rat)—human        antibody chain;    -   an antibody chain having a human heavy chain variable region        upstream of a non-human vertebrate (e.g., mouse or rat) light        chain constant region;    -   an antibody chain having a human light chain variable region        upstream of a non-human vertebrate (e.g., mouse or rat) heavy        chain constant region.

The invention also relates to a transgene encoding a plurality of humanIgH V regions, one or more human D regions and one or more human Jregions upstream of a host non-human mammal light chain constant region,optionally comprised within a vector.

The invention also relates to a transgene encoding a plurality of humanIg light chain V regions, and one or more human light chain J regionsupstream of a host non-human mammal heavy chain constant region,optionally comprised within a vector.

In one aspect the invention relates to a cell, or non-human mammal, thegenome of which comprises: one or more human Ig light chain kappa Vregions and one or more human Ig light chain kappa J regions upstream ofall or part of the human kappa constant region.

In another aspect the invention relates to a cell, or non-human mammal,the genome of which comprises: one or more human Ig light chain lambda Vregions and one or more human Ig light chain lambda J regions upstreamof all or part of the human lambda constant region.

Suitably the light chain VJ and C regions are able to form antibodychains in vivo capable of specifically reacting with an antigen.

In one aspect of the invention there is no non-human coding sequence inthe inserted light chain region.

In such aspects a human kappa and/or lambda region is inserted into thegenome, in combination with insertion of the heavy chain VDJ region orpart thereof, upstream of the host heavy chain constant region asdisclosed herein.

The cell or non-human mammal of the invention may comprise:

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region; and    -   (b) one or more human Ig light chain kappa V regions and one or        more human Ig light chain kappa J regions upstream of all or        part of the non-human kappa constant region, wherein the        non-human mammal is able to produce a repertoire of antibodies        having an antibody chain comprising non-human mammal constant        region and a human variable region.

The cell or non-human mammal of the invention may comprise

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region; and    -   one or more human Ig light chain lambda V regions and one or        more human Ig light chain lambda J regions upstream of the host        non-human mammal lambda constant region; wherein the non-human        mammal is able to produce a repertoire of antibodies having an        antibody chain comprising a non-human mammal constant region and        a human variable region.

Suitably the insertion of the human VJC light chain DNA, or part thereofas disclosed above, is made at the equivalent mouse locus. In one aspectthe human light chain kappa VJC DNA, or part thereof, is insertedimmediately upstream or downstream of the mouse kappa VJC region. In oneaspect, the human light chain lambda VJC region or part thereof isinserted immediately upstream or downstream of the mouse lambda VJCregion. In one aspect only the human kappa VJC locus is inserted and notthe human lambda VJC locus. In one aspect only the human lambda VJClocus is inserted and not the human kappa VJC locus. Insertions may bemade using the techniques disclosed herein, and suitably do not removethe host sequences from the genome. In one aspect the non-human mammalhost VJC sequences may be inactivated in some way, by mutation, orinversion, or by insertion of the human variable region DNA, or by anyother means. In one aspect the cell or non-human mammal of the inventionmay comprise an insertion of the complete VJC human region.

The human kappa variable region DNA might be inserted into the genome infunctional arrangement with a lambda constant region, for exampleinserted upstream of a lambda constant region. Alternatively humanlambda region variable DNA might be inserted in functional arrangementwith a kappa constant region, for example inserted upstream of a kappaconstant region.

In one aspect one or more non-human mammal control sequences such as theenhancer sequence(s) is maintained upstream of the nonhuman mammal Muconstant region, suitably in its native position with respect to thedistance from the constant region.

In one aspect one or more non-human mammal control sequences such as anenhancer sequence(s) are maintained downstream of the nonhuman mammal Muconstant region, suitably in its native position with respect to thedistance from the constant region.

In one aspect a non-human mammal switch sequence, suitably theendogenous switch sequence, is maintained upstream of the non-humanmammal Mu constant region, suitably in its native position with respectto distance from the constant region.

In such location the host enhancer or switch sequences are operative invivo with the host constant region sequence(s).

In one aspect a switch sequence is neither human, nor native in thenon-human mammal, for example in one aspect a non-human mammal switchsequence is not a mouse or human switch sequence. The switch sequencemay be, for example, a rodent or primate sequence, or a syntheticsequence. In particular the switch sequence may be a rat sequence wherethe non-human mammal is a mouse. By way of example, a mouse or humanconstant mu sequence may be placed under the control of a switchsequence from a rat, or chimp, or other switch sequence, suitablycapable of allowing isotype switching to occur in vivo.

In one aspect the switch sequence of the invention is a switch sequencecomprising 3, 4, 5, 6 or more (up to 82) contiguous repeats of therepeat sequence GGGCT (SEQ ID no 46-50), such as a rat switch sequence.By “rat switch” herein it is meant that the switch is a wild-type switchcorresponding to a switch from a rat genome or derived from such aswitch.

In one aspect the switch sequence of the invention is a rat switchsequence comprising the following repeats: GAGCT (296 repeats; SEQ ID No18), GGGGT (50 repeats; SEQ ID No 19), and GGGCT (83 repeats; SEQ ID No20).

In one example the rat switch sequence comprises or consists of thesequence of SEQ ID no 1.

In these embodiments, and where the non-human mammal is a mouse or thecell is a mouse cell, the switch is optionally a rat switch as describedherein.

Alternatively, the switch sequence present in cells or mammal of theinvention is a mouse switch, eg, is from a mouse such as a mouse 129strain or mouse C57 strain, or from a strain derived therefrom,optionally comprising or consisting of the sequence of SEQ ID no 4 or 5.By “mouse switch” herein it is meant that the switch is a wild-typeswitch corresponding to a switch from a mouse genome or derived fromsuch a switch. In this embodiment, and where the non-human mammal is amouse or the cell is a mouse cell, the mouse switch sequence isoptionally the endogenous switch or is a mouse switch from another mousestrain.

The cell or mammal of the invention may therefore comprise a human ornon-human mammal switch sequence and a human or non-human mammalenhancer region or regions. They may be upstream of a human or non-humanmammal constant region. Preferably the control sequences are able todirect expression or otherwise control the production of antibodiescomprising a constant region with which they are associated. Onecombination envisaged is a rat switch with mouse enhancer sequences andmouse constant regions in a mouse cell.

In one aspect the invention relates to a cell, preferably a non-humancell, or non-human mammal comprising an immunoglobulin heavy chain orlight chain locus having DNA from 3 or more species. For example, thecell or animal may comprise host cell constant region DNA, one or morehuman V, D or J coding sequences and one or more non-human, non-host DNAregions that are able to control a region of the immunoglobulin locus,such as a switch sequence, promoter or enhancer which are able tocontrol expression or isotype switching in vivo of the Ig DNA. In oneaspect the cell or animal is a mouse and comprises additionally humanDNA from the human Ig locus and additionally a non-mouse DNA sequence,such as a rat DNA sequence, capable of regulation of the mouse or humanDNA.

In another aspect the invention relates to a cell, preferably non-humancell, or non-human mammal comprising an immunoglobulin heavy chain orlight chain locus having DNA from 2 or more different human genomes. Forexample, it could comprise heavy chain V(D)J sequences from more thanone human genome within a heavy or light chain, or heavy chain VDJ DNAfrom one genome and light chain VJ sequences from a different genome.

In one aspect the invention relates to a DNA fragment or cell ornon-human mammal comprising an immunoglobulin heavy chain or light chainlocus, or part thereof, having DNA from 2 or more species, where onespecies contributes a non-coding region such as a regulatory region, andthe other species coding regions such as V, D, J or constant regions.

In one aspect the human promoter and/or other control elements that areassociated with the different human V, D or J regions are maintainedafter insertion of the human VDJ into the mouse genome.

In a further aspect one or more of the promoter elements, or othercontrol elements, of the human regions, such as the human V regions, areoptimised to interact with the transcriptional machinery of a non-humanmammal.

Suitably a human coding sequence may be placed under the control of anappropriate non-human mammal promoter, which allows the human DNA to betranscribed efficiently in the appropriate non-human animal cell. In oneaspect the human region is a human V region coding sequence, and a humanV region is placed under the control of a non-human mammal promoter.

The functional replacement of human promoter or other control regions bynon-human mammal promoter or control regions may be carried out by useof recombineering, or other recombinant DNA technologies, to insert apart of the human Ig region (such as a human V region) into a vector(such as a BAC) containing a non-human Ig region. Therecombineering/recombinant technique suitably replaces a portion of thenon-human (e.g. mouse) DNA with the human Ig region, and thus places thehuman Ig region under control of the non-human mammal promoter or othercontrol region. Suitably the human coding region for a human V regionreplaces a mouse V region coding sequence. Suitably the human codingregion for a human D region replaces a mouse D region coding sequence.Suitably the human coding region for a human J region replaces a mouse Jregion coding sequence. In this way human V, D or J regions may beplaced under the control of a non-human mammal promoter, such as a mousepromoter.

In one aspect the only human DNA inserted into the non-human mammaliancell or animal are V, D or J coding regions, and these are placed undercontrol of the host regulatory sequences or other (non-human, non-host)sequences, In one aspect reference to human coding regions includes bothhuman introns and exons, or in another aspect simply exons and nointrons, which may be in the form of cDNA.

It is also possible to use recombineering, or other recombinant DNAtechnologies, to insert a non-human-mammal (e.g. mouse) promoter orother control region, such as a promoter for a V region, into a BACcontaining a human Ig region. A recombineering step then places aportion of human DNA under control of the mouse promoter or othercontrol region.

The approaches described herein may also be used to insert some or allof the V, D and J regions from the human heavy chain upstream of a lightchain constant region, rather than upstream of the heavy chain constantregion. Likewise some or all of the human light chain V and J regionsmay be inserted upstream of the heavy chain constant region. Insertionmay be at the endogenous constant region locus, for example between theendogenous constant and J region, and may be of some, or all, of the V,D or J genes alone, excluding promoter or enhancer sequences, or may beof some, or all, of the V, D or J genes with one or more or allrespective promoter or enhancer sequences. In one aspect the fullrepertoire of V, D or J fragments in germline orientation may beinserted upstream and in functional arrangement with a host constantregion.

Thus the present invention allows V and/or D and/or J regions from ahuman, or any species, to be inserted into a chromosome of a cell from adifferent species that comprises a constant region, allowing a chimaericantibody chain to be expressed.

In one aspect the invention requires only that some human variableregion DNA is inserted into the genome of a non-human mammal in operablearrangement with some, or all, of the human heavy chain constant regionat the region of the endogenous heavy chain constant region locus suchthat an antibody chain can be produced. In this aspect of the inventionand where human light chain DNA is additionally inserted, the lightchain DNA insertion can be in the form of a completely human construct,having both human variable DNA and human constant region DNA, or havehuman variable region DNA and constant region DNA from a non-human,non-host species. Other variations are also possible, such as insertionof both of the light chain human variable region and host genomeconstant region. In addition the insertion of said light chaintransgenes need not be at the equivalent endogenous locus, but may beanywhere in the genome. In such a scenario the cell or mammal mayproduce chimaeric heavy chains (comprising human variable region DNA andmouse constant region DNA) and light chains comprising human variableand human constant region DNA. Thus in one aspect of the invention thelambda and or kappa human variable region DNA can be inserted upstreamof the endogenous locus, or downstream, or indeed on a differentchromosome to the endogenous locus, and inserted with or withoutconstant region DNA.

As well insertion of human light chain DNA upstream of the hostnon-human mammal constant region, a further aspect of the inventionrelates to insertion of one or both light chain human variable regionsdownstream of the equivalent endogenous locus constant region, orelsewhere in the genome.

Generally, insertion of human variable region DNA at or close to theequivalent endogenous locus in the recipient genome is preferred, forexample within 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 kb of the boundary(upstream or downstream) of a host immunoglobulin locus.

Thus in one aspect the invention can relate to a cell or non-humanmammal whose genome comprises:

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region; and    -   (b) one or more human Ig light chain kappa V regions and one or        more human Ig light chain kappa J regions, and/or, one or more        human Ig light chain lambda V regions and one or more human Ig        light chain lambda J regions;        wherein the non-human mammal is able to produce a repertoire of        chimaeric antibodies, or chimaeric light or heavy chains, having        a non-human mammal constant region and a human variable region.

In one particular aspect the genome of the cell or non-human mammalcomprises:

-   -   a plurality of human IgH V regions, one or more human D regions        and one or more human J regions upstream of the host non-human        mammal constant region;    -   one or more human Ig light chain kappa V regions and one or more        human Ig light chain kappa J regions upstream of the host        non-human mammal kappa constant region, and    -   one or more human Ig light chain lambda V regions and one or        more human Ig light chain lambda J regions downstream of the        host non-human mammal lambda constant region,    -   optionally in which the human lambda variable region may be        inserted upstream or downstream of the endogenous host lambda        locus in operable linkage with a human lambda constant region,        such that the non-human mammal or cell can produce fully human        antibody light chains and chimaeric heavy chains.

In a further, different, aspect of the invention, the use of the methodsof the invention allows a locus to be built up in a stepwise manner bysequential insertions, and thus allows for the insertion of humanvariable DNA together with human or non-human constant region DNA at anysuitable location in the genome of a non-human host cell. For example,methods of the invention can be used to insert human immunoglobulinvariable region DNA together with constant region DNA from the hostgenome anywhere in the genome of a non-human host cell, allowing achimaeric antibody chain to be produced from a site other than theendogenous heavy region. Any human heavy chain or light chain DNAconstruct contemplated above can be inserted into any desired positioninto the genome of a non-human host cell using the techniques describedherein. The present invention thus also relates to cells and mammalshaving genomes comprising such insertions.

The invention also relates to a vector, such as a BAC, comprising ahuman V, D or J region in a functional arrangement with a non-humanmammal promoter, or other control sequence, such that the expression ofthe human V, D or J region is under the control of the non-human mammalpromoter in a cell of the non-human mammal, such as an ES cell, inparticular once inserted into the genome of that cell.

The invention also relates to cells and non-human mammals containingsaid cells, which cells or mammals have a human V, D or J region in afunctional arrangement with a non-human mammal promoter, or othercontrol sequence, such that the expression of the human V, D or J regionis under the control of the non-human mammal promoter in the cells ormammal.

Generally, one aspect of the invention thus relates to a non-humanmammal host cell capable of expression of a human V, D or J codingsequence under the control of a host promoter or control region, theexpression capable of producing a humanised antibody having a humanvariable domain and non-human mammal constant region.

In one aspect the invention relates to a cell, such as a non mammaliancell, such as an ES cell, the genome of which comprises

-   -   (a) a plurality of human IgH V regions, one or more human D        regions and one or more human J regions upstream of the host        non-human mammal constant region; and    -   (b) optionally one or more human Ig light chain kappa V regions        and one or more human Ig light chain kappa J regions upstream of        the host non-human mammal kappa constant region and/or one or        more human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region;

In another aspect the invention relates to a cell, such as a non-humanmammal cells, such as ES cells whose genome comprises

-   -   (a) a plurality of human Ig light chain kappa V regions and one        or more human Ig light chain kappa J regions upstream of the        host non-human mammal kappa constant region and/or a plurality        of human Ig light chain lambda V regions and one or more human        Ig light chain lambda J regions upstream of the host non-human        mammal lambda constant region; and    -   (b) optionally one or more human IgH V regions, one or more        human D regions and one or more human J regions upstream of the        host non-human mammal constant region

In one aspect the cell is an ES cell is capable of developing into anon-human mammal able to produce a repertoire of antibodies which arechimaeric, said chimaeric antibodies having a non-human mammal constantregion and a human variable region. Optionally the genome of the cell ismodified to prevent expression of fully host-species specificantibodies.

In one aspect the cell is an induced pluripotent stem cell (iPS cell).

In one aspect cells are isolated non-human mammalian cells.

In one aspect a cell as disclosed herein is preferably a non-humanmammalian cell.

In one aspect the cell is a cell from a mouse strain selected fromC57BL/6, M129 such as 129/SV, BALB/c, and any hybrid of C57BL/6, M129such as 129/SV, or BALB/c.

The invention also relates to a cell line which is grown from orotherwise derived from cells as described herein, including animmortalised cell line. The cell line may comprise inserted human V, Dor J genes as described herein, either in germline configuration orafter rearrangement following in vivo maturation. The cell may beimmortalised by fusion (eg, electrofusion or using PEG according tostandard procedures) to a tumour cell (eg, P3X63-Ag8.653 (obtainablefrom LGC Standards; CRL-1580), SP2/0-Ag14 (obtainable from ECACC), NSIor NS0), to provide an antibody producing cell and cell line, or be madeby direct cellular immortalisation.

The present invention also relates to vectors for use in the invention.In one aspect such vectors are BACs (bacterial artificial chromosomes).It will be appreciated that other cloning vectors may be used in theinvention, and therefore reference to BACs herein may be taken to refergenerally to any suitable vector.

In one aspect BACs used for generation of human DNA to be inserted, suchas the VDJ or VJ regions are trimmed so that in the final human VDJ orVJ region or part thereof in the non-human mammal, no sequence isduplicated or lost when compared to the original human genomic sequence.

In one aspect the invention relates to a vector comprising an insert,preferably comprising a region of human DNA from some of the human VDJor VJ locus, flanked by DNA which is not from that locus. The flankingDNA may comprise one or more selectable markers or one or more sitespecific recombination sites. In one aspect the vector comprises 2 ormore, such as 3, heterospecific and incompatible site specificrecombination sites. In one aspect the site specific recombination sitesmay be loxP sites, or variants thereof, or FRT sites or variantsthereof. In one aspect the vector comprises one or more transposon ITR(inverted terminal repeat) sequences.

In one aspect the non-human animals of the invention suitably do notproduce any fully humanised antibodies. In one aspect this is becausethere is no DNA inserted from the human constant region. Alternativelythere is no human constant region DNA in the genome capable of formingan antibody in conjunction with the inserted human variable region DNAcomponent, for example due to mutation within any human constant regionDNA or distance from any constant region human DNA and human variableregion DNA.

In one aspect human light chain constant region DNA may be included inthe cell genome, such that a fully human lambda or kappa human antibodychain might be generated, but this would only be able to form anantibody with a chimaeric heavy chain, and not produce a fully humanantibody having human variable and constant regions.

In one aspect the non-human mammal genome is modified to preventexpression of fully host-species specific antibodies. Fully host speciesspecific antibodies are antibodies that have both variable and constantregions from the host organism. In this context the term ‘specific’ isnot intended to relate to the binding of the antibodies produced by thecells or animals of the invention but rather to the origin of the DNAwhich encodes those antibodies.

In one aspect the non-human mammal genome is modified to preventexpression of the native (fully host species specific) antibodies in themammal by inactivation of all or a part of the host non-human mammal Igloci. In this context, inactivation or prevention of endogenous antibodyor gene segment usage (using any inactivation technique describedherein) is, for example, substantially complete inactivation orprevention (substantially 100%, ie, essentially none (eg, less than 10,5, 4, 3, 2, 1 or 0.5%) of the endogenous antibody chain (eg, noendogenous heavy chains) is expressed). This can be determined, forexample, at the antibody chain (protein) level by assessing the antibodyrepertoire produced by the non-human vertebrate, mammal or at thenucleotide level by assessing mRNA transcripts of antibody chain loci,eg, using RACE. In an embodiment, inactivation is more than 50% (ie, 50%or less of the antibodies or transcripts are of an endogenous antibodychain), 60%, 70%, 80%, 85%, 90%, 95%, 96%, 97%, 98% or 99%. For example,in an embodiment, endogenous heavy chain expression is substantiallyinactivated such that no more than 85%, 90%, 95%, 96%, 97%, 98% or 99%of the heavy chain repertoire of the vertebrate (mammal) is provided byendogenous heavy chains. For example, endogenous heavy chain expressionis substantially inactivated such that substantially none of the heavychain repertoire of the vertebrate (mammal) is provided by endogenousheavy chains. For example, in an embodiment, endogenous heavy chainexpression is substantially inactivated such that no more than 85%, 90%,95%, 96%, 97%, 98% or 99% of the kappa chain repertoire of thevertebrate (mammal) is provided by endogenous kappa chains. For example,endogenous kappa chain expression is substantially inactivated such thatsubstantially none of the kappa chain repertoire of the vertebrate(mammal) is provided by endogenous kappa chains. For example, in anembodiment, endogenous heavy chain expression is substantiallyinactivated such that no more than 85%, 90%, 95%, 96%, 97%, 98% or 99%of the lambda chain repertoire of the vertebrate (mammal) is provided byendogenous lambda chains. For example, endogenous lambda chainexpression is substantially inactivated such that substantially none ofthe lambda chain repertoire of the vertebrate (mammal) is provided byendogenous lambda chains.

In one aspect this is achieved by inversion of all or part of thenon-human mammal VDJ region, or VJ region, optionally by insertion ofone or more site specific recombinase sites into the genome and then useof these sites in recombinase-mediated excision or inversion of all or apart of the non-human mammal Ig locus. In one aspect a double inversion,may be employed, the first to move the V(D)Js away from the endogenouslocus and then a more local inversion which puts them in the correctorientation. In one aspect a single loxP site is used to invert thenon-human mammal VDJ region to a centromeric locus or telomeric locus.

In one example, a mouse or mouse cell of the invention comprisesinverted endogenous heavy chain gene segments (eg, VH, D and JH, such asthe entire endogenous heavy chain VDJ region) that are immediately 3′ ofposition 119753123, 119659458 or 120918606 on an endogenous mousechromosome 12. Optionally, the genome of the mouse or cell is homozygousfor said chromosome 12.

The invention also provides:—

A cassette for inversion and inactivation of endogenous non-humanvertebrate (eg, mouse or rat) antibody chain gene segments, the segmentsbeing part of an antibody chain locus sequence on a chromosome of anon-human vertebrate (eg, mouse or rat) cell (eg, ES cell) wherein thesequence is flanked at its 3′ end by a site-specific recombination site(eg, lox, rox or frt), the cassette comprising a nucleotide sequenceencoding an expressible label or selectable marker and a compatiblesite-specific recombination site (eg, lox, rox or frt) flanked by a 5′and a 3′ homology arm, wherein the homology arms correspond to or arehomologous to adjacent stretches of sequence in the cell genome on adifferent chromosome or on said chromosome at least 10, 15, 20, 25, 30,35, 40, 45 or 50 mb away from the endogenous gene segments.

The invention also provides:—

A cassette for inversion and inactivation of endogenous mouse antibodyheavy chain gene segments, the segments being part of a heavy chainlocus sequence on chromosome 12 of a mouse cell (eg, ES cell) whereinthe sequence is flanked at its 3′ end by a site-specific recombinationsite (eg, lox, rox or frt), the cassette comprising a nucleotidesequence encoding an expressible label or selectable marker and acompatible site-specific recombination site (eg, lox, rox or frt)flanked by a 5′ and a 3′ homology arm, wherein the homology armscorrespond to or are homologous to adjacent stretches of sequence in themouse cell genome on a different chromosome or on chromosome 12 at least10, 15, 20, 25, 30, 35, 40, 45 or 50 mb away from the endogenous genesegments.

The invention provides:—

A cassette for inversion and inactivation of endogenous mouse antibodyheavy chain gene segments, the segments being part of a heavy chainlocus sequence on chromosome 12 of a mouse cell (eg, ES cell) whereinthe sequence is flanked at its 3′ end by a site-specific recombinationsite (eg, lox, rox or frt), the cassette comprising a nucleotidesequence encoding an expressible label or selectable marker and acompatible site-specific recombination site (eg, lox, rox or frt)flanked by a 5′ and a 3′ homology arm, wherein (i) the 5′ homology armis mouse chromosome 12 DNA from coordinate 119753124 to coordinate119757104 and the 3′ homology arm is mouse chromosome 12 DNA fromcoordinate 119749288 to 119753123; or (ii) the 5′ homology arm is mousechromosome 12 DNA from coordinate 119659459 to coordinate 119663126 andthe 3′ homology arm is mouse chromosome 12 DNA from coordinate 119656536to 119659458; or (iii) the 5′ homology arm is mouse chromosome 12 DNAfrom coordinate 120918607 to coordinate 120921930 and the 3′ homologyarm is mouse chromosome 12 DNA from coordinate 120915475 to 120918606.

-   -   Embodiment (i) results in an inversion of mouse chromosome 12        from coordinate 119753123 to coordinate 114666436.    -   Embodiment (ii) results in an inversion of mouse chromosome 12        from coordinate 119659458 to coordinate 114666436    -   Embodiment (iii) results in an inversion of mouse chromosome 12        from coordinate 12091806 to coordinate 114666436.

Thus, the invention provides a mouse or mouse cell whose genomecomprises an inversion of a chromosome 12, wherein the inversioncomprises inverted endogenous heavy chain gene segments (eg, VH, D andJH, such as the entire endogenous heavy chain VDJ region); wherein themouse comprises a transgenic heavy chain locus comprising a plurality ofhuman VH gene segments, a plurality of human D segments and a pluralityof human JH segments operably connected upstream of an endogenousconstant region (eg, C mu) so that the mouse or cell (optionallyfollowing differentiation into a B-cell) is capable of expressing anantibody comprising a variable region comprising sequences derived fromthe human gene segments; and wherein the inversion is (i) an inversionof mouse chromosome 12 from coordinate 119753123 to coordinate114666436; (ii) an inversion of mouse chromosome 12 from coordinate119659458 to coordinate 114666436; or (iii) an inversion of mousechromosome 12 from coordinate 12091806 to coordinate 114666436.

In one embodiment, the endogenous gene segments are from a 129-derivedmouse cell (eg, segments from an AB2.1 cell) and the homology arms areisogenic DNA (ie, identical to 129-derived endogenous sequencesdemarcated by the respective coordinates stated in (i) to (iii) above).Thus, no new sequence is created by homologous recombination using thesehomology arms. In another embodiment, the arms are from a mouse strainthat is different from the endogenous strain. The site-specificrecombination sites are mutually compatible and mutually inverted suchthat, on expression of an associated recombinase enzyme (eg, Cre, Dre orFlp), recombination between the site in the inserted inversion cassetteand the site flanking the endogenous gene segments is carried out,thereby inverting and moving the endogenous gene segments far upstream(5′) of their original location in the heavy chain locus. Thisinactivates endogenous heavy chain expression. Similarly, light chaininactivation can be performed by choosing the homology arms of theinversion cassette with reference to a chromosomal region spaced atleast 10, 15, 20, 25, 30, 35, 40, 45 or 50 mb away from the endogenouslight chain locus, the latter comprising a site-specific recombinationsite that is compatible with the site in the inversion cassette.

In one embodiment, the expressible label is a fluorescent label, eg, GFPor a variant thereof (eg, YFP, CFP or RFP). Thus, a label is usedinstead of a selection marker, such as one that confers resistance toallow for selection of transformants.

The invention provides a method of inactivating gene segments of anendogenous antibody locus, the method comprising

-   -   (i) Providing a non-human vertebrate cell (eg, an ES cell, eg, a        mouse ES cell) whose genome comprises an antibody chain locus        comprising endogenous variable region gene segments;    -   (ii) Targeting a site-specific recombination site to flank the        3′ of the 3′-most of said endogenous gene segments;    -   (iii) Targeting a second site-specific recombination site at        least 10 mb away from said endogenous gene segments, the second        site being compatible with the first site inverted with respect        to the first site;    -   (iv) Expressing a recombinase compatible with said sites to        effect site-specific recombination between said sites, thereby        inverting and moving said gene segments away from said locus,        wherein the endogenous gene segments are inactivated; and    -   (v) Optionally developing the cell into a progeny cell or        vertebrate (eg, mouse or rat) whose genome is homozygous for the        inversion.

The genome of the progeny cell or vertebrate can comprise transgenicheavy and/or light chain loci, each capable of expressing antibodychains comprising human variable regions. Optionally, endogenous heavyand kappa light chain expression is inactivated by inverting endogenousheavy and kappa variable region gene segments according to the method ofthe invention. Optionally, endogenous lambda chain expression is alsoinactivated in this way.

In an alternative to the method and inversion cassettes of theinvention, instead of inverting and moving variable region gene segmentsonly, other parts of the endogenous locus can alternatively oradditionally be inverted and moved to effect inactivation. For example,one or more endogenous regulatory elements (eg, Smu and/or Emu) and/orone or more endogenous constant regions (eg, Cmu and/or Cgamma) can beinverted and moved.

Sites that “flank” in the above contexts of the invention can beprovided such that a site-specific recombination site immediately flanksthe endogenous sequence or is spaced therefrom, eg, by no more than 250,200, 250, 100, 50 or 20 kb in the 3′ direction.

In one aspect the non-human mammal genome into which human DNA isinserted comprises endogenous V, (D) and J regions, and the endogenoussequences have not been deleted.

The invention comprises a method for insertion of multiple DNA fragmentsinto a DNA target, suitably to form a contiguous insertion in which theinserted fragments are joined together directly without interveningsequences. The method is especially applicable to the insertion of alarge DNA fragment into a host chromosome which can be carried out in astepwise fashion.

In one aspect the method comprises insertion of a first DNA sequenceinto a target, the sequence having a DNA vector portion and a firstsequence of interest (X1); insertion of a second DNA sequence into thevector portion of the first sequence, the second DNA sequence having asecond sequence of interest (X2) and a second vector portion; and thenexcising any vector sequence DNA separating X1 and X2 to provide acontiguous X1X2, or X2X1 sequence within the target. There is optionallyinsertion of a further one or more DNA sequences, each DNA sequencehaving a further sequence of interest (X3, . . . ) and a further vectorportion, into the vector portion of the preceding DNA sequence, to buildup a contiguous DNA fragment in the target.

The DNA target for insertion of the first DNA sequence may be a specificsite or any point in the genome of a particular cell.

The general method is described herein in relation to the insertion ofelements of the human VDJ region, but is applicable to insertion of anyDNA region, from any organism, and in particular insertion of large DNAfragments of >100 kB, such as 100-250 kb, or even larger, such as thatof the TCR or HLA. Features and approaches described herein in respectof the VDJ insertion may be equally applied to the any of the methodsdisclosed

In one aspect the inserted DNA is human DNA, such as the human VDJ or VJregion, is built up in the genome of a cell, such as an ES cell, in astepwise manner using 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20or more separate insertions for each heavy chain or light chain region.Fragments are suitably inserted at the same or substantially the samecell locus, e.g. ES cell locus, one after another, to form the completeVDJ or VJ region, or part thereof. The present invention also relates tocells and non-human animals comprising intermediates in the processwhose genomes may comprise only a partial VDJ region, such as only humanvariable region DNA.

In a further aspect the method for producing a transgenic non-humanmammal comprises the insertion of human VDJ or VJ regions upstream ofthe host non-human mammal constant region by step-wise insertion ofmultiple fragments by homologous recombination, preferably using aniterative process. Suitably fragments of approximately 100 KB from thehuman VDJ and VJ locus are inserted, suitably to form part of, or acomplete, VDJ or VJ region after the final iteration of the insertionprocess, as disclosed herein.

In one aspect the insertion process commences at a site where aninitiation cassette has been inserted into the genome of a cell, such asan ES cell, providing a unique targeting region. In one aspect theinitiation cassette is inserted in the non-human mammal heavy chainlocus, for use in insertion of human heavy chain DNA. Similarly aninitiation cassette may be inserted in the non-human mammal light chainlocus, for use in insertion of human light chain VJ DNA The initiationcassette suitably comprises a vector backbone sequence with which avector having a human DNA fragment in the same backbone sequence canrecombine to insert the human DNA into the cell (e.g. ES) cell genome,and suitably a selection marker, such as a negative selection marker.Suitably the vector backbone sequence is that of a BAC library, to allowBACs to be used in the construction of the ES cells and mammals. Thevector backbone sequence may however be any sequence which serves as atarget site into which a homologous sequence can insert, for example byhomologous recombination, for example RMCE, and is preferably not DNAencoding any of the VDJ or constant region.

In one aspect the insertion of the first DNA fragment into an initiationcassette is followed by insertion of a second DNA fragment into aportion of the first DNA fragment, suitably a part of the vectorbackbone of the second DNA fragment. In one aspect an inserted DNAfragment comprises a part of the human VDJ region flanked by 5′ and/or3′ sequences that are not from the human VDJ region. In one aspect the5′ and/or 3′ flanking sequences may each contain one or more selectablemarkers, or be capable of creating a selectable system once insertedinto the genome. In one aspect one or both flanking sequences may beremoved from the genome in vitro, or in vivo, following insertion. Inone aspect the method comprises insertion of a DNA fragment followed byselection of both 5′ and 3′ ends of the inserted fragment flanking thehuman VDJ DNA. In one aspect the iterative insertion is made byinsertion of DNA fragments at the 5′ end of the previous insertedfragment, and in this aspect there may be deletion in vivo of the vectorDNA which separates the inserted human DNA sequences, to provide acontiguous human DNA sequence.

In one aspect insertion of human VDJ DNA into a genome may be achievedwithout leaving any flanking DNA in the genome, for example bytransposase mediate DNA excision. One suitable transposase is thePiggybac transposase.

In one aspect the first human variable region fragment is inserted byhomologous recombination at the initiation cassette backbone sequenceand then the DNA of any negative selection marker and initiationcassette are subsequently removed by recombination between recombinasetarget sequences, such as FRT using in this example, FLPase expression.Generally repeated targeted insertions at the (e.g. BAC) backboneinitiation sequence and subsequent removal by rearrangement betweenrecombinase target sequences are repeated to build up the entire humanVDJ region upstream of the host non-mammal constant region.

In one aspect a selectable marker or system may be used in the method.The marker may be generated upon insertion of a DNA fragment into agenome, for example forming a selectable marker in conjunction with aDNA element already present in the genome.

In one aspect the cell (e.g. ES) cell genome does not contain 2identical selectable markers at the same time during the process. It canbe seen that the iterative process of insertion and selection can becarried out using only 2 different selection markers, as disclosed inthe examples herein, and for example the third selectable marker may beidentical to the first marker, as by the time of insertion of the thirdvector fragment the first vector fragment and the first marker has beenremoved.

In one aspect a correct insertion event, is confirmed before moving tothe next step of any multistep cloning process, for example byconfirmation of BAC structure using high density genomic arrays toscreen ES cells to identify those with intact BAC insertions, sequencingand PCR verification.

Initiation cassette (also called a “landing pad”)

The invention also relates to a polynucleotide ‘landing pad’ sequence,the polynucleotide comprising nucleic acid regions homologous to regionsof a target chromosome to allow for insertion by homologousrecombination into the target chromosome, and comprising a nucleic acidsite which permits recombinase-driven insertion of nucleic acid into thelanding pad. The invention also relates to vectors, cells and mammals ofthe invention comprising a landing pad as disclosed herein inserted intothe genome of the cell.

The landing pad optionally comprises a non-endogenous S-mu, e.g. a ratS-mu switch

The landing pad optionally comprises (in 5′ to 3′ orientation) a mouseEμ sequence, a non-human, non-mouse (e.g. rat) Switch p and at least aportion of a mouse Cμ or the entire mouse Cμ.

The rat switch sequence optionally comprises or consists of SEQ ID NO 1.

The landing pad optionally comprises the 5′ homology arm of SEQ ID NO 6.

The landing pad optionally has the sequence of SEQ ID 2 or SEQ ID NO 3.

In one embodiment, the landing pad comprises an expressible label. Forexample the label is a fluorescent label, eg, GFP or a variant thereof(eg, YFP, CFP or RFP). Thus, a label is used instead of a selectionmarker (such as one that confers resistance to allow for selection oftransformants).

In an embodiment, the landing pad comprises 5′ and 3′ homology arms forinsertion into the cell genome using homologous recombination. Thehomology arms can be isogenic DNA (eg, identical to 129-derivedendogenous sequences of when a 129-derived ES cell is used). Thus, nonew sequence is created by homologous recombination using these homologyarms. In another embodiment, the arms are from a mouse strain that isdifferent from the endogenous strain (ES cell strain).

The methods of the invention include methods wherein the landing padsequence comprises any of the configurations or sequences as disclosedherein.

Another method of the invention comprises the step of insertion of thelanding pad into a mouse chromosome by homologous recombination betweenmouse J1-4 and mouse C mu sequences.

Another method of the invention comprises the step of insertion of thelanding pad into the mouse chromosome 12 by homologous recombinationbetween mouse J1-4 and E mu.

In one aspect the method uses site specific recombination for insertionof one or more vectors into the genome of a cell, such as an ES cell.Site specific recombinase systems are well known in the art and mayinclude Cre-lox, and FLP/FRT or combinations thereof, in whichrecombination occurs between 2 sites having sequence homology.

Additionally or alternatively to any particular Cre/Lox or FLP/FRTsystem described herein, other recombinases and sites that may be usedin the present invention include Dre recombinase, rox sites, and PhiC31recombinase.

Suitable BACs are available from the Sanger centre, see “A genome-wide,end-sequenced 129Sv BAC library resource for targeting vectorconstruction”. Adams D J, Quail M A, Cox T, van der Weyden L, Gorick BD, Su Q, Chan W I, Davies R, Bonfield J K, Law F, Humphray S, Plumb B,Liu P, Rogers J, Bradley A. Genomics. 2005 December; 86(6):753-8. Epub2005 Oct. 27. The Wellcome Trust Sanger Institute, Hinxton,Cambridgeshire CB10 1SA, UK. BACs containing human DNA are alsoavailable from, for example, Invitrogen™. A suitable library isdescribed in Osoegawa K et al, Genome Research 2001. 11: 483-496.

In one aspect a method of the invention specifically comprises:

-   -   (1) insertion of a first DNA fragment into a non-human ES cell,        the fragment containing a first portion of human VDJ or VJ        region DNA and a first vector portion containing a first        selectable marker;    -   (2) optionally deletion of the a part of the first vector        portion;    -   (3) insertion of a second DNA fragment into a non-human ES cell        containing the first DNA fragment, the insertion occurring        within the first vector portion, the second DNA fragment        containing a second portion of the human VDJ or VJ region and a        second vector portion containing a second selectable marker,    -   (4) deletion of the first selectable marker and first vector        portion, preferably by a recombinase enzyme action;    -   (5) insertion of a third DNA fragment into a non-human ES cell        containing the second DNA fragment, the insertion occurring        within the second vector portion, the third DNA fragment        containing a third portion of the human VDJ or VJ region and a        third vector portion containing third selectable marker,    -   (6) deletion of the second selectable marker and second vector        portion; and    -   (7) iteration of the steps of insertion and deletion, as        necessary, for fourth and further fragments of the human VDJ or        VJ human regions, as necessary, to produce an ES cell with a        part or all of the human VDJ or VJ region inserted as disclosed        herein, and suitably to remove all the vector portions within        the ES cell genome.

In another aspect the invention comprises

-   -   (1) insertion of DNA forming an initiation cassette into the        genome of a cell;    -   (2) insertion of a first DNA fragment into the initiation        cassette, the first DNA fragment comprising a first portion of a        human DNA and a first vector portion containing a first        selectable marker or generating a selectable marker upon        insertion;    -   (3) optionally removal of part of the vector DNA    -   (4) insertion of a second DNA fragment into the vector portion        of the first DNA fragment, the second DNA fragment containing a        second portion of human DNA and a second vector portion, the        second vector portion containing a second selectable marker, or        generating a second selectable marker upon insertion;    -   (5) optionally, removal of any vector DNA to allow the first and        second human DNA fragments to form a contiguous sequence; and    -   (6) iteration of the steps of insertion of human VDJ DNA and        vector DNA removal, as necessary, to produce a cell with all or        part of the human VDJ or VJ region sufficient to be capable of        generating a chimaeric antibody in conjunction with a host        constant region,        wherein the insertion of one, or more, or all of the DNA        fragments uses site specific recombination.

In one aspect the non-human mammal is able to generate a diversity of atleast 1×10⁶ different functional chimaeric immunoglobulin sequencecombinations.

In one aspect the targeting is carried out in ES cells derived from themouse C57BL/6N, C57BL/6J, 129S5 or 129Sv strain.

In one aspect non-human animals, such as mice, are generated in aRAG-1-deficient or a RAG-2-deficient background, or other suitablegenetic background which prevents the production of mature host B and Tlymphocytes.

In one aspect the non-human mammal is a rodent, suitably a mouse, andcells of the invention, are rodent cells or ES cells, suitably mouse EScells.

The ES cells of the present invention can be used to generate animalsusing techniques well known in the art, which comprise injection of theES cell into a blastocyst followed by implantation of chimaericblastocystys into females to produce offspring which can be bred andselected for homozygous recombinants having the required insertion. Inone aspect the invention relates to a chimeric animal comprised of EScell-derived tissue and host embryo derived tissue. In one aspect theinvention relates to genetically-altered subsequent generation animals,which include animals having a homozygous recombinants for the VDJand/or VJ regions.

In a further aspect the invention relates to a method for producing anantibody specific to a desired antigen the method comprising immunizinga transgenic non-human mammal as above with the desired antigen andrecovering the antibody (see e.g. Harlow, E. & Lane, D. 1998, 5^(th)edition, Antibodies: A Laboratory Manual, Cold Spring Harbor Lab. Press,Plainview, N.Y.; and Pasqualini and Arap, Proceedings of the NationalAcademy of Sciences (2004) 101:257-259). Suitably an immunogenic amountof the antigen is delivered. The invention also relates to a method fordetecting a target antigen comprising detecting an antibody produced asabove with a secondary detection agent which recognises a portion ofthat antibody.

In a further aspect the invention relates to a method for producing afully humanised antibody comprising immunizing a transgenic non-humanmammal as above with the desired antigen, recovering the antibody orcells expressing the antibody, and then replacing the non-human mammalconstant region with a human constant region. This can be done bystandard cloning techniques at the DNA level to replace the non-humanmammal constant region with an appropriate human constant region DNAsequence—see e.g. Sambrook, J and Russell, D. (2001, 3'd edition)Molecular Cloning: A Laboratory Manual (Cold Spring Harbor Lab. Press,Plainview, N.Y.).

In a further aspect the invention relates to humanised antibodies andantibody chains produced according to the present invention, both inchimaeric and fully humanised form, and use of said antibodies inmedicine. The invention also relates to a pharmaceutical compositioncomprising such an antibodies and a pharmaceutically acceptable carrieror other excipient.

Antibody chains containing human sequences, such as chimaerichuman—non-human antibody chains, are considered humanised herein byvirtue of the presence of the human protein coding regions region. Fullyhumanised antibodies may be produced starting from DNA encoding achimaeric antibody chain of the invention using standard techniques.

Methods for the generation of both monoclonal and polyclonal antibodiesare well known in the art, and the present invention relates to bothpolyclonal and monoclonal antibodies of chimaeric or fully humanisedantibodies produced in response to antigen challenge in non-humanmammals of the present invention.

In a yet further aspect, chimaeric antibodies or antibody chainsgenerated in the present invention may be manipulated, suitably at theDNA level, to generate molecules with antibody-like properties orstructure, such as a human variable region from a heavy or light chainabsent a constant region, for example a domain antibody; or a humanvariable region with any constant region from either heavy or lightchain from the same or different species; or a human variable regionwith a non-naturally occurring constant region; or human variable regiontogether with any other fusion partner. The invention relates to allsuch chimaeric antibody derivatives derived from chimaeric antibodiesidentified according to the present invention.

In a further aspect, the invention relates to use of animals of thepresent invention in the analysis of the likely effects of drugs andvaccines in the context of a quasi-human antibody repertoire.

The invention also relates to a method for identification or validationof a drug or vaccine, the method comprising delivering the vaccine ordrug to a mammal of the invention and monitoring one or more of: theimmune response, the safety profile; the effect on disease.

The invention also relates to a kit comprising an antibody or antibodyderivative as disclosed herein and either instructions for use of suchantibody or a suitable laboratory reagent, such as a buffer, antibodydetection reagent.

The invention also relates to a method for making an antibody, or partthereof, the method comprising providing:

-   -   (i) a nucleic acid encoding an antibody, or a part thereof,        obtained according to the present invention; or    -   (ii) sequence information from which a nucleic acid encoding an        antibody obtained according to the present invention, or part        thereof, can be expressed to allow an antibody to be produced.

The present invention also relates to a chimaeric antibody comprising ahuman variable region and a non-human vertebrate or mammal (optionally arat or mouse) constant region (optionally a C gamma or C mu), whereinthe antibody is encoded by a nucleotide sequence corresponding to thenucleotide sequence of a chimaeric heavy chain locus of a cell(optionally a B-cell, ES cell or hybridoma), the locus comprising anon-human vertebrate constant region nucleotide sequence and arearranged VDJ nucleotide sequence produced by the in vivo rearrangementof a human V region, a human D region and a human J region, the V regionbeing selected from one of a V1-3 region, V2-5 region, V4-4 region, V1-2region or V6-1 region, and optionally a V1-3 or V6-1 segment.Optionally, the J region is any of JH1, JH2, JH3, JH4, JH5 or JH6, andin one aspect is JH4 or JH6. The D region is, in one aspect, any D3-9,D3-10, D6-13 or D6-19. In one example, rearranged VDJ nucleotidesequence is produced by the in vivo rearrangement of human V1-3 and JH4(optionally with D3-9, D3-10, D6-13 or D-19); or V1-3 and JH6(optionally with D3-9, D3-10, D6-13 or D-19); or V6-1 and JH4(optionally with D3-9, D3-10, D6-13 or D-19); or V6-1 and JH6(optionally with D3-9, D3-10, D6-13 or D-19). In one example therearranged VDJ nucleotide sequence is produced by the in vivorearrangement of human V6-1 DH3-10, V1-3 DH3-10, V1-3 DH6-19, V1-3 Dh3-9or V6-1 DH6-19. In one aspect the antibody comprises any combinationexemplified in the Examples and Figures herein. Optionally, the in vivorearrangement is in a cell (eg, B cell or ES cell) derived from the samenon-human vertebrate species as the constant region sequence (eg, amouse B cell or ES cell). The invention also relates to a non-humanvertebrate or mammal cell (eg, a B-cell or ES cell or hybridoma) whosegenome comprises a chimaeric heavy chain locus as described above inthis paragraph. The invention also relates to a non-human vertebrate ormammal (eg, a mouse or rat) whose genome comprises a chimaeric heavychain locus as described above in this paragraph.

The present invention also relates to a non-human vertebrate or mammalhaving a genome encoding a chimaeric antibody, the chimaeric antibodycomprising a human variable region and a non-human vertebrate or mammal(optionally a rat or mouse) constant region (optionally a C gamma or Cmu), the mammal:

-   -   expressing more V1-3 antibodies than V2-5, V4-4, V1-2 or V6-1        antibodies; and/or    -   expressing more V1-3 JH4 or V1-3 JH6 antibodies than any of,        individually, V1-3 JH1, V1-3 JH2, V1-3 JH3 or V1-3 JH5        antibodies, and/or    -   expressing more V6-1 JH4 or V6-1 JH6 antibodies than any of,        individually, V6-1 JH1, V6-1 JH2, V6-1 JH3 or V6-1 JH5        antibodies and/or    -   expressing a greater number of V1-3 DH3-10 antibodies than        antibodies V1-3 with any other D region. Expression of        antibodies can be assessed by methods readily available to the        skilled person and as conventional in the art. For example,        expression can be assessed at the mRNA level as shown in the        examples below.

The invention also relates to a chimaeric antibody comprising a humanvariable region and a non-human vertebrate or mammal (optionally a rator mouse) constant region (optionally a light chain constant region),wherein the antibody is obtainable from a mammal (optionally a rat ormouse) whose genome comprises an antibody chain locus comprising agermline human kappa V1-8 and germline human kappa J1 sequence, andwherein the antibody is obtainable by in vivo recombination in saidmammal of the V1-8 and J1 sequences and wherein the antibody has avariable region sequence which is different from that which is encodedby germline human kappa V1-8 and germline human kappa J1sequences. Thus,in this aspect of the invention the human germline sequences are able toundergo productive rearrangement to form a coding sequence which, inconjunction with the non-human constant region sequence, can beexpressed as a chimaeric antibody chain having at least a complete humanvariable region and a non-human constant region. This is in contrast (asthe examples show below) to the combination of the germline human kappaV1-8 and germline human kappa J1 sequences per se, which do not providefor an antibody coding sequence (due to the inclusion of stop codons).In one aspect the rearranged sequence of the chimaeric antibody is aresult of somatic hypermutation. In one aspect the antibody is a kappaantibody; in another aspect the antibody comprises a non-human heavychain constant region (eg, a rat or mouse C gamma or C mu). The antibodysequence optionally comprises a X₁X₂ T F G Q, where X₁X₂=PR, RT, or PW(SEQ ID No 21); optionally a X₁X₂ T F G Q G T K V E I K R A D A (SEQ IDNo 22) motif. Such motifs are not found in the equivalent position inthe germline sequence as shown in the examples. The invention alsorelates to a non-human vertebrate or mammal cell (eg, a B-cell or EScell or hybridoma) whose genome comprises a chimaeric antibody chainlocus as described above in this paragraph. The invention also relatesto a non-human vertebrate or mammal (eg, a mouse or rat) whose genomecomprises a chimaeric antibody chain locus as described above in thisparagraph.

The invention also relates to a chimaeric antibody comprising a humanvariable region and a non-human vertebrate or mammal (optionally a rator mouse) constant region (optionally a light chain constant region),wherein the antibody is obtainable from a mammal (optionally a rat ormouse) whose genome comprises an antibody chain locus comprising agermline human kappa V1-6 and germline human kappa J1 sequence, andwherein the antibody is obtainable by in vivo recombination in saidmammal of the V1-6 and J1 sequences and wherein the antibody has avariable region sequence which is different from that which is encodedby germline human kappa V1-6 and germline human kappa J1sequences. Thus,in this aspect of the invention the human germline sequences are able toundergo productive rearrangement to form a coding sequence which, inconjunction with the non-human constant region sequence, can beexpressed as a chimaeric antibody chain having at least a complete humanvariable region and a non-human constant region. This is in contrast (asthe examples show below) to the combination of the germline human kappaV1-6 and germline human kappa J1 sequences per se, which do not providefor an antibody coding sequence (due to the inclusion of stop codons).In one aspect the rearranged sequence of the chimaeric antibody is aresult of somatic hypermutation. In one aspect the antibody is a kappaantibody; in another aspect the antibody comprises a non-human heavychain constant region (eg, a rat or mouse C gamma or C mu). The antibodysequence optionally comprises a X₃X₄ T F G Q, where X₃X₄=PR or PW (SEQID No 23); optionally a X₃X₄ T F G Q G T K V E I K R A D A (SEQ ID No24) motif. Such motifs are not found in the equivalent position in thegermline sequence as shown in the examples. The invention also relatesto a non-human vertebrate or mammal cell (eg, a B-cell or ES cell orhybridoma) whose genome comprises a chimaeric antibody chain locus asdescribed above in this paragraph. The invention also relates to anon-human vertebrate or mammal (eg, a mouse or rat) whose genomecomprises a chimaeric antibody chain locus as described above in thisparagraph.

The invention also relates to a chimaeric antibody comprising a humanvariable region and a non-human (optionally a rat or mouse) constantregion (optionally a C gamma or C mu or a C kappa), wherein the antibodyis obtainable from a mammal (optionally a rat or mouse) whose genomecomprises an antibody chain locus comprising a germline human kappa V1-5and germline human kappa J1 sequence, and wherein the antibody isobtainable by in vivo recombination in said mammal of the V1-5 and J1sequences. The invention also relates to a non-human vertebrate ormammal cell (eg, a B-cell or ES cell or hybridoma) whose genomecomprises a chimaeric antibody chain locus as described above in thisparagraph. The invention also relates to a non-human vertebrate ormammal (eg, a mouse or rat) whose genome comprises a chimaeric antibodychain locus as described above in this paragraph.

The invention also relates to a chimaeric antibody comprising a humanvariable region and a non-human (optionally a rat or mouse) constantregion (optionally a C gamma or C mu or a C kappa), wherein the antibodyis obtainable from a mammal (optionally a rat or mouse) whose genomecomprises an antibody chain locus comprising a germline human kappa V1-5and germline human kappa J4 sequence, and wherein the antibody isobtainable by in vivo recombination in said mammal of the V1-5 and J4sequences. The invention also relates to a non-human vertebrate ormammal cell (eg, a B-cell or ES cell or hybridoma) whose genomecomprises a chimaeric antibody chain locus as described above in thisparagraph. The invention also relates to a non-human vertebrate ormammal (eg, a mouse or rat) whose genome comprises a chimaeric antibodychain locus as described above in this paragraph.

Antibodies of the invention may be isolated, in one aspect beingisolated from the cell or organism in which they are expressed.

A non-human mammal whose genome comprises:

-   -   (a) the human IgH VDJ region upstream of the host non-human        mammal constant region; and    -   (b) the human Ig light chain kappa V and J regions upstream of        the host non-human mammal kappa constant region and/or the human        Ig light chain lambda V and J regions upstream of the host        non-human mammal lambda constant region;        wherein the non-human mammal is able to produce a repertoire of        chimaeric antibodies having a non-human mammal constant region        and a human variable region,        and optionally wherein the non-human mammal genome is modified        to prevent expression of fully host-species specific antibodies.

A non-human mammal ES cell whose genome comprises:

-   -   (a) the human IgH V, D and J region upstream of a non-human        mammal constant region; and    -   (b) the human Ig locus light chain kappa V and J regions        upstream of the host non-human mammal kappa constant region,        and/or the human Ig locus light chain lambda V and J regions        upstream of the host non-human mammal lambda constant region        wherein the ES cell is capable of developing into a non-human        mammal, being able to produce a repertoire of antibodies which        are chimaeric, having a non-human mammal constant region and a        human variable region.

A method for producing a transgenic non-human mammal able to produce arepertoire of chimaeric antibodies, the antibodies having a non-humanmammal constant region and a human variable region, the methodcomprising inserting by homologous recombination into a non-human mammalES cell genome

-   -   (a) the human IgH VDJ region upstream of the host non-human        mammal heavy chain constant region, and    -   (b) the human IgL VJ region for lambda or kappa chains upstream        of the host non-human mammal lambda or kappa chain constant        region, respectively such that the non-human mammal is able to        produce a repertoire of chimaeric antibodies having a non-human        mammal constant region and a human variable region, wherein        steps (a) and (b) can be carried out in either order and each of        steps (a) and (b) can be carried out in a stepwise manner or as        a single step.

In one aspect the insertion of human VDJ or VJ regions upstream of thehost non-human mammal constant region is accomplished by step-wiseinsertion of multiple fragments by homologous recombination.

In one aspect the step-wise insertions commence at a site where aninitiation cassette has been inserted into the genome of an ES cellproviding a unique targeting region consisting of a BAC backbonesequence and a negative selection marker.

In one aspect the first human variable region fragment is inserted byhomologous recombination at the initiation cassette BAC backbonesequence and said negative selection marker and initiation cassette aresubsequently removed by recombination between recombinase targetsequences.

In one aspect repeated targeted insertions at the BAC backboneinitiation sequence and subsequent removal of the backbone byrearrangement between recombinase target sequences is repeated to buildup the entire human VDJ region upstream of the host non-mammal constantregion.

Insertion of human variable region gene segments precisely within theendogenous mouse JH4-Cmu intron

There is further provided a cell or non human mammal according to theinvention wherein the mammal is a mouse or the cell is a mouse cell andwherein the insertion of the human heavy chain DNA is made in a mousegenome between coordinates 114,667,091 and 114,665,190 of mousechromosome 12.

There is further provided a cell or non human mammal according to theinvention wherein the insertion of the human heavy chain DNA is made atcoordinate 114,667,091.

There is further provided a cell or non human mammal according to theinvention wherein the human IgH VDJ region comprises nucleotides105,400,051 to 106,368,585 from human chromosome 14 (coordinates referto NCBI36 for the human genome).

There is further provided a method, cell or non human mammal accordingto the invention wherein a human coding region DNA sequence is in afunctional arrangement with a non-human mammal control sequence, suchthat transcription of the human DNA is controlled by the non-humanmammal control sequence. In one example, the initiation cassette isinserted between the mouse J4 and C alpha exons. There is furtherprovided an initiation cassette suitable for use in the methodcomprising a vector backbone sequence and a selection marker.

Non-Human Vertebrates Expressing Kappa & Lambda Variable Regions

(i) K and L Chains Produced in Human-Like Ratios

This aspect of the invention is useful for producing light chains thatare not skewed to non-human-like ratios. For example, in mice kappa-typelight chains predominate by far over lambda-type light chains (typicallyof the order of 95% kappa light chains: 5% lambda light chains in awild-type mouse). Humans, on the other hand, typically display around60% kappa: around 40% lambda. Thus, lambda expression is much higherthan found in a mouse. It would be desirable to provide a non-humanvertebrate, such as a mouse or a rat, in which a higher proportion oflambda-type light chains can be expressed. This is useful when thevertebrate expresses light chains bearing human lambda variable regionsand other light chains bearing human kappa variable regions. To thisend, the inventors have demonstrated for the first time such avertebrate that expresses elevated lambda light chains, and thus theinvention provides:—

A non-human vertebrate (eg, a mouse or rat) whose genome comprises an Iggene segment repertoire produced by targeted insertion of human Ig genesegments into one or more endogenous Ig loci, the genome comprisinghuman Vλ and Jλ gene segments provided by insertion into an endogenouslight chain locus of the vertebrate upstream of a constant region, thegenome comprising human Vκ and Jκ gene segments provided by insertioninto an endogenous light chain locus of the vertebrate upstream of aconstant region, wherein the vertebrate expresses immunoglobulin lightchains comprising kappa light chain variable regions and immunoglobulinlight chains comprising lambda light chain variable regions, whereinmore than 20% of the light chains expressed by the vertebrate compriselambda variable regions (eg, as determined by FACS of splenic B-cells).

The remaining light chains express kappa variable regions.

WO03047336 teaches the desirability of producing human-like kappa:lambdaratios, but this does not provide an enabled or plausible disclosure ofhow to achieve this.

(ii) K and L Chains Produced with Normal B-Cell Compartments

The inventors have successfully generated non-human vertebratescontaining targeted insertion of human V and J lambda gene segments toenable expression of light chains comprising human lambda variableregions by normal (ie, comparable to wild-type vertebrate) B-cellcompartments. Thus, the inventors have provided such vertebrates thatcan usefully produce such light chains with good repertoires and morereliably than prior art transgenic non-human vertebrates that displaycomprised B-cell compartments of reduced size and maturity, and indeedwhich may not even produce light chains having human lambda variableregions. Thus, the invention provides:—

A non-human vertebrate (eg, a mouse or rat) whose genome comprises an Iggene segment repertoire produced by targeted insertion of human Ig genesegments into one or more endogenous Ig loci, the genome comprisinghuman Vλ and Jλ gene segments provided by insertion into an endogenouslight chain locus of the vertebrate upstream of a constant region, thegenome comprising human Vκ and Jκ gene segments provided by insertioninto an endogenous light chain locus of the vertebrate upstream of aconstant region, wherein the vertebrate expresses immunoglobulin lightchains comprising kappa light chain variable regions and immunoglobulinlight chains comprising lambda light chain variable regions, and whereinthe vertebrate produces a normal proportion or percentage of maturesplenic B-cells (eg, as determined by FACS of splenic B-cells).

With regard to non-human vertebrates (i) and (ii), the followingembodiments are contemplated (unless specified, each embodiment appliesto (i) or (ii)):—

In an embodiment, the human Vλ and Jλ insertion comprises at least thefunctional human V and J gene segments comprised by a human lambda chainIg locus from Vλ3-27 to Cλ7.

In an embodiment, the human Vλ and Jλ insertion comprises at least humanV gene segments Vλ3-27, Vλ3-25, Vλ2-23, Vλ3-22, Vλ3-21, Vλ3-19, Vλ2-18,Vλ3-16, Vλ2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3 and Vλ3-1.

In an embodiment, the human Vλ and Jλ insertion comprises one, more orall of human J gene segments Jλ1, Jλ2, Jλ3, Jλ6 and Jλ7.

In an embodiment, the human Vλ and Jλ insertion comprises an insertionof a human Jλ-Cλ cluster, wherein the cluster comprises the J and C genesegments from Jλ1 to Cλ7.

In an embodiment, the human Vλ and Jλ insertion comprises an insertionof a human Eλ enhancer. For example, the Eλ enhancer is provided ingermline configuration with respect to a human Jλ7 that is alsocomprised by the insertion. For example, the Eλ enhancer is provided ingermline configuration with respect to a human Jλ-Cλ cluster that isalso comprised by the insertion, wherein the cluster comprises Jλ1 toCλ7 in human germline configuration. In a human germline configurationthe Eλ enhancer is 3′ of the Jλ-Cλ cluster.

In an embodiment or vertebrate (i) or (ii), the human Vλ and Jλinsertion is provided by an insertion of a sequence corresponding tocoordinates 22886217 to 23327884 of human chromosome 22.

In an embodiment or vertebrate (ii), the human Vλ and Jλ insertion isprovided by an insertion of a sequence corresponding to coordinates23064876 to 23327884 of human chromosome 22.

In an embodiment, the human Vκ and Jκ insertion comprises at least thefunctional human V and J gene segments comprised by a human kappa chainIg locus from Vκ1-33 to Jκ5.

In an embodiment, the human Vκ and Jκ insertion comprises at least humanV gene segments Vκ1-33, Vκ2-30, Vκ2-29, Vκ2-28, Vκ1-27, Vκ2-24, Vκ3-20,Vκ1-17, Vκ1-16, Vκ3-15, Vκ1-13, Vκ1-12, Vκ3-11, Vκ1-9, Vκ1-8, Vκ1-6,Vκ1-5, Vκ5-2 and Vκ4-1.

In an embodiment, the human Vκ and Jκ insertion comprises one, more orall of human J gene segments Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5.

In an embodiment, more than 30, 35, 40, 45 or 50% of the light chainsexpressed by the vertebrate comprise lambda variable regions.

In an embodiment, from 20 to 40, 45 or 50% of the light chains expressedby the vertebrate comprise lambda variable regions. In an embodiment,from 30 to 40, 45 or 50% of the light chains expressed by the vertebratecomprise lambda variable regions.

In an embodiment, said kappa light chain variable regions are humankappa light chain variable regions.

In an embodiment, the human Vκ and Jκ gene segments are in an endogenouskappa light chain locus of the vertebrate upstream of a kappa constantregion.

In an embodiment, the human Vλ and Jλ gene segments are in an endogenouskappa light chain locus of the vertebrate.

In an embodiment, the human Vλ and Jλ gene segments are in an endogenouslambda light chain locus of the vertebrate.

In an embodiment, the vertebrate expresses light chains comprising humankappa variable regions and expresses light chains comprising humanlambda variable regions. In an example, endogenous (non-humanvertebrate) kappa chain expression is substantially inactive or isinactive and/or endogenous (non-human vertebrate) lambda chainexpression is substantially inactive or is inactive. Where thevertebrate is a mouse, mouse lambda chain expression is typically verylow (around 5% or less) and in this case it may not be necessary toengineer the mouse genome to further inactivate endogenous lambda chainexpression. Thus, where the vertebrate is s mouse, endogenous kappachain expression is substantially inactive or is inactive and mouselambda chain expression is 5% or less of all light chain expression.

In an embodiment, the vertebrate produces a normal proportion orpercentage of mature splenic B-cells. For example, this can bedetermined by FACS of splenic B-cells isolated from the vertebrate.

In an embodiment, the vertebrate produces a normal ratio of T1, T2 andmature splenic B-cells. For example, this can be determined by FACS ofsplenic B-cells isolated from the vertebrate.

In an embodiment, at least 40, 50, 60 or 70% of total splenic B-cellsproduced by the vertebrate are mature B-cells. For example, this can bedetermined by FACS of splenic B-cells isolated from the vertebrate.

One embodiment described herein is a non-human vertebrate or a non-humanvertebrate cell (e.g., a mouse, rat, mouse cell or a rat cell) whosegenome comprises an Ig gene segment repertoire produced by targetedinsertion of human Ig gene segments into one or more endogenous Ig loci,the genome comprising a targeted insertion of human immunoglobulin Vλ,Jλ and Cλ gene segments into an endogenous non-human vertebrate kappa orlambda light chain locus upstream of an endogenous non-human vertebratekappa or lambda constant region for expression of a human VJC lightchain. In one aspect, the human immunoglobulin Vλ, Jλ and Cλ insertionof the vertebrate or cell comprises at least the functional human V, Jand C gene segments including a human lambda chain Ig locus from Vλ3-1to Cλ7.

One embodiment described herein is a non-human vertebrate or cell (e.g.,a mouse, rat, mouse cell or a rat cell) having a genome comprising arecombinant immunoglobulin light chain locus, the locus comprising atargeted insertion that comprises human immunoglobulin Vλ and Jλ genesegments, wherein the human Vλ and Jλ gene segments are positionedupstream to a light chain constant region and comprise at least thefunctional V and J gene segments from Vλ2-18 to Cλ7 of a human lambdalight chain locus, and wherein the vertebrate or cell expressesimmunoglobulin light chains comprising human lambda variable regions.

In one aspect of an embodiment of a vertebrate or cell described herein,the endogenous kappa chain expression is substantially inactive. In oneaspect of an embodiment of a vertebrate or cell described herein, theendogenous lambda chain expression is substantially inactive. In oneaspect of an embodiment of a vertebrate or cell described herein, thegenome is homozygous for the targeted insertion of human Vλ and Jλ genesegments. In one aspect of an embodiment of a vertebrate or celldescribed herein, the endogenous light chain locus is an endogenouskappa locus. In one aspect of an embodiment of a vertebrate or celldescribed herein, the endogenous light chain locus is an endogenouslambda locus. In one aspect of an embodiment of a vertebrate or celldescribed herein, the human Vλ and Jλ are downstream of endogenous Vλand Jλ gene segments. In one aspect of an embodiment of a vertebrate orcell described herein, the targeted insertion is positioned within 100kb of an endogenous light chain locus enhancer sequence. In one aspectof an embodiment of a vertebrate or cell described herein, the targetedinsertion comprises a human light chain enhancer.

In one aspect of an embodiment of a vertebrate or cell described herein,the human light chain enhancer is an Eλ sequence and wherein the Eλsequence is positioned between the human Jλ gene segments and anendogenous light chain constant region.

In one aspect of an embodiment of a vertebrate or cell described herein,the vertebrate or cell expresses lambda light chains comprising arepertoire of human lambda variable regions encoded by human Vλ and Jλgene segments, wherein the human Vλ comprises gene segment Vλ3-1 andoptionally one or more of Vλ3-16, V2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9,Vλ2-8, and Vλ4-3, wherein the human Vλ and Jλ gene segments are includedin the targeted insertion.

In one aspect of an embodiment of a vertebrate or cell described herein,the vertebrate or cell expresses lambda light chains comprising arepertoire of human lambda variable regions encoded by human Vλ and Jλgene segments, wherein the human Vλ comprises gene segment Vλ2-14 and,optionally, one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11,Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3, and Vλ3-1, wherein the human Vλ and Jλ genesegments are included in the targeted insertion.

In one aspect of an embodiment of a vertebrate or cell described herein,the vertebrate or cell expresses lambda light chains comprising arepertoire of human lambda variable regions encoded by human Vλ and Jλgene segments, wherein the human Vλ comprises gene segment Vλ2-8 and,optionally, one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11,Vλ3-10, Vλ3-9, Vλ4-3, and Vλ3-1, wherein the human Vλ and Jλ genesegments are included in the targeted insertion.

In one aspect of an embodiment of a vertebrate or cell described herein,the vertebrate or cell expresses lambda light chains comprising arepertoire of human lambda variable regions encoded by human Vλ and Jλgene segments, wherein the human Vλ comprises gene segment Vλ3-10 and,optionally, one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11,Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3, and Vλ3-1, wherein the human Vλ and Jλ genesegments are included in the targeted insertion. In one aspect, at leastVλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3, andVλ3-1 are included in the targeted insertion.

In one aspect of an embodiment of a vertebrate or cell described herein,an endogenous kappa enhancer is present; optionally wherein theendogenous enhancer comprises an iEκ and/or 3′ Eκ sequence.

In one aspect of an embodiment of a vertebrate or cell described herein,less than 10% of immunoglobulin light chains expressed by saidvertebrate or cell comprises endogenous kappa variable regions.

In one aspect of an embodiment of a vertebrate or cell described herein,the locus comprises endogenous VK and JK gene segments upstream to thetargeted insert, wherein the targeted insert comprises at least thefunctional Vλ and Jλ gene segments from Vλ3-1 to Cλ7 of a human lambdalight chain immunoglobulin locus, and wherein expression of light chainscomprising endogenous kappa variable regions derived from recombinationof endogenous VK and JK gene segments is substantially inactive.

One embodiment described herein is a non-human vertebrate or a non-humanvertebrate cell, the genome of which the endogenous IgK-VJ has beenmoved away from the endogenous Eκ enhancer, thereby inactivatingendogenous IgK-VJ regions.

One embodiment described herein is a non-human vertebrate or a non-humanvertebrate cell whose genome comprises an Ig gene segment repertoireproduced by targeted insertion of human Ig gene segments into one ormore endogenous Ig loci, the genome comprising the following light chainloci arrangement

-   -   (a) L at one endogenous kappa chain allele and K at the other        endogenous kappa chain allele; or    -   (b) L at one endogenous lambda chain allele and Kat the other        endogenous lambda chain allele; or    -   (c) L at both endogenous kappa chain alleles;    -   (d) L at both endogenous lambda chain alleles;    -   (e) L at one endogenous kappa chain allele and the other        endogenous kappa allele has been inactivated; or    -   (f) L at one endogenous lambda chain and the other endogenous        lambda chain allele has been inactivated;        wherein

L represents a human lambda gene segment insertion comprising at leastthe functional human Vλ and Jλ, of the human lambda chain Ig locus fromVλ3-1 to Cλ7; and optionally further comprising Cλ gene segments, and

K represents a human Vκ and Jκ insertion;

wherein in the genome the human gene segments are inserted upstream of aconstant region for expression of light chains comprising variableregions derived from the recombination of human V and J gene segments.

One embodiment described herein is a non-human vertebrate (e.g., a mouseor rat) that expresses immunoglobulin heavy chains comprising humanvariable regions, wherein essentially all the heavy chains expressed bythe non-human vertebrate comprise human variable regions; wherein saidheavy chains comprising human variable regions are expressed as part ofserum IgG1, IgG2b and IgM (and optionally IgG2a) antibodies in themouse; the vertebrate comprising an immunoglobulin heavy chain locuscomprising human VH, DH and JH gene segments upstream of a vertebrateconstant region. In one aspect of an embodiment of a vertebratedescribed herein, the vertebrate expresses a normal relative proportionof serum IgG1, IgG2a, IgG2b and IgM antibodies. In one aspect of anembodiment of a vertebrate described herein, the vertebrate expresses:

-   -   (i) serum IgG1 at a concentration of about 25-350 μg/ml;    -   (ii) serum IgG2a at a concentration of about 0-200 n/ml;    -   (iii) serum IgG2b at a concentration of about 30-800 n/ml; and    -   (iv) serum IgM at a concentration of about 50-300 n/ml;        or    -   (i) serum IgG 1 at a concentration of about 10-600 n/ml;    -   (ii) serum IgG2a at a concentration of about 0-500 n/ml;    -   (iii) serum IgG2b at a concentration of about 20-700 n/ml; and    -   (iv) serum IgM at a concentration of about 50-700 n/ml;        as determined by Ig capture on a plate followed by incubation        with anti-non-human vertebrate isotype-specific labelled        antibodies and quantification of Ig using the label.

In one aspect of the veterbrate described herein, the vertebrateproduces a normal proportion or percentage of mature splenic B-cellsand/or a normal proportion or percentage of bone marrow B-cellprogenitor cells.

Described herein is a method for expressing immunoglobulin heavy chainscomprising human variable regions, wherein essentially all the heavychains expressed comprise human variable regions; comprising exposing avertebrate described herein to antigen, wherein the heavy chainscomprising human variable regions are expressed as part of serum IgG1,IgG2b and IgM (and optionally IgG2a) antibodies in the vertebrate.

Described herein is a method for expressing immunoglobulin light chainscomprising human variable regions, wherein essentially all the lightchains expressed comprise human lambda variable regions derived fromrecombination of human Vλ and Jλ gene segments comprising exposing thevertebrate described herein to antigen, wherein said vertebrate producesa normal proportion or percentage of mature splenic B-cells and/or anormal proportion or percentage of bone marrow B-cell progenitor cells.

Described herein is a method for expressing immunoglobulin heavy chainscomprising human variable regions, wherein essentially all the heavychains expressed comprise human variable regions comprising exposing thevertebrate described herein to antigen, wherein the vertebrate producesa normal proportion or percentage of mature splenic B-cells and/or anormal proportion or percentage of bone marrow B-cell progenitor cells.

In one embodiment of a vertebrate or cell described herein, the genomeof the vertebrate or cell comprises

-   -   (i) L at an endogenous lambda allele; and    -   (ii) L at an endogenous kappa allele.

In one aspect of the vertebrate or cell described herein, the genomecomprises L at both endogenous kappa alleles and/or L at both endogenouslambda alleles. The endogenous kappa light chain expression issubstantially inactive in one aspect. The endogenous lambda light chainexpression is substantially inactive in one aspect. In one aspect of thevertebrate or cell described herein, the L represents a human lambdagene segment insertion that comprises at least human V gene segmentsVλ3-27, Vλ3-25, Vλ2-23, Vλ3-22, Vλ3-21, Vλ3-19, Vλ2-18, Vλ3-16, Vλ2-14,Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3 and Vλ3-1. In one aspect ofthe vertebrate or cell described herein, the L represents a human lambdagene segment insertion that comprises at least human J gene segmentsJλ1, Jλ2, Jλ3, Jλ6 and Jλ7.

Another embodiment described herein, is a non-human vertebrate whosegenome comprises an Ig gene segment repertoire produced by targetedinsertion of human Ig gene segments into one or more endogenous Ig loci,the genome comprising human Vλ and Jλ gene segments inserted into anendogenous light chain locus of the vertebrate upstream of a constantregion; the genome comprising human VK and JK gene segments insertedinto an endogenous light chain locus of the vertebrate upstream of aconstant region, wherein the vertebrate expresses immunoglobulin lightchains comprising kappa light chain variable regions and immunoglobulinlambda light chain variable regions, wherein more than 20% of the lightchains expressed by the vertebrate comprise lambda variable regions, asdetermined by FACS analysis of B cells isolated from the vertebrate. Inone aspect, the remaining light chains express kappa variable regions asdetermined by FACS.

Another embodiment described herein is a non-human vertebrate whosegenome comprises an Ig gene segment repertoire produced by targetedinsertion of human Ig gene segments into one or more endogenous Ig loci,the genome comprising human Vλ and Jλ gene segments inserted into anendogenous light chain locus of the vertebrate upstream of a constantregion, the genome comprising human VK and JK gene segments insertedinto an endogenous light chain locus of the vertebrate upstream of aconstant region, wherein the vertebrate expresses immunoglobulin lightchains comprising kappa light chain variable regions and immunoglobulinlight chains comprising lambda light chain variable regions, and whereinthe vertebrate produces a normal proportion of percentage of maturesplenic B-cells, as determined by FACS analysis of B cells isolated fromthe vertebrate.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vλ and Jλ insertion comprises at least the functional human V andJ gene segments comprised by a human lambda chain Ig locus from Vλ3-27to Cλ7.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vλ and Jλ insertion comprises at least human V gene segmentsVλ3-27, Vλ3-25, Vλ2-23, Vλ3-22, Vλ3-21, Vλ3-19, Vλ2-18, Vλ3-16, Vλ2-14,Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, V4λ-3 and Vλ3-1.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vλ and Jλ insertion comprises one, more or all of human J genesegments Jλ1, Jλ2, Jλ3, Jλ6 and Jλ7.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vκ and Jκ insertion comprises at least the functional human V andJ gene segments comprised by a human kappa chain Ig locus from Vκ1-33 toJκ5.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vκ and Jκ insertion comprises at least human V gene segmentsVκ1-33, Vκ2-30, Vκ2-29, Vκ2-28, Vκ1-27, Vκ2-24, Vκ3-20, Vκ1-17, Vκ1-16,Vκ3-15, Vκ1-13, Vκ1-12, Vκ3-11, Vκ1-9, Vκ1-8, Vκ1-6, Vκ1-5, Vκ5-2 andVκ4-1.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vκ and Jκ insertion comprises one, m more or all of human J genesegments Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5.

In one aspect of an embodiment of a vertebrate described herein, thepercentage of the light chains expressed by the vertebrate comprisinglambda antibody variable regions, is selected from the group consistingof at least 30%, at least 35%, at least 40%, at least 45% and at least50%.

In one aspect of an embodiment of a vertebrate described herein, thekappa light chain variable regions are human kappa light chain variableregions.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vκ and Jκ gene segments are in an endogenous kappa light chainlocus of the vertebrate upstream of a kappa constant region.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vλ and Jλ gene segments are positioned in an endogenous kappalight chain locus of the vertebrate.

In one aspect of an embodiment of a vertebrate described herein, thehuman Vλ and Jλ gene segments are positioned in an endogenous lambdalight chain locus of the vertebrate.

In one aspect of an embodiment of a vertebrate described herein, thevertebrate expresses light chains comprising human kappa variableregions and expresses light chains comprising human lambda variableregion.

In one aspect of an embodiment of a vertebrate described herein, theendogenous kappa chain expression is inactive.

In one aspect of an embodiment of a vertebrate described herein, theendogenous lambda chain expression is inactive

In one aspect of an embodiment of a vertebrate described herein, thevertebrate produces a normal proportion or percentage of mature splenicB-cells, as determined by FACS.

In one aspect of an embodiment of a vertebrate described herein, thevertebrate produces a normal ratio of T1, T2 and mature splenic B-cells,as determined by FACS.

In one aspect of an embodiment of a vertebrate described herein, atleast 40, 50, 60 or 70% of total splenic B-cells produced by thevertebrate are mature B-cells, as determined by FACS.

Described herein is a method for producing an antibody or light chaincomprising a lambda variable region specific to a desired antigen, themethod comprising immunizing a vertebrate described herein with thedesired antigen and recovering the antibody or light chain or recoveringa cell producing the antibody or light chain.

One embodiment of the method further comprises humanizing said antibodyor antibody light chain comprising replacing the non-human vertebrateconstant region with a human constant region, optionally by engineeringof the nucleic acid encoding the antibody or light chain.

Described herein is a humanised antibody or antibody light chainproduced according to said method, or a derivative thereof.

Also described herein is a pharmaceutical composition comprising thehumanised antibody or chain produced according to the methods describedherein, and a pharmaceutically acceptable carrier.

The invention provides the following aspects (starting at aspect number103):—

-   103. A cell or non human mammal according to any one of the above    configurations, examples, embodiments or aspects, wherein the mammal    is a mouse or the cell is a mouse cell and wherein the insertion of    the human heavy chain DNA is made in a mouse genome between    coordinates 114,667,091 and 114,665,190 of mouse chromosome 12.-   104. A cell or non human mammal according to any one of the above    configurations, examples, embodiments or aspects, wherein the    insertion of the human heavy chain DNA is made at coordinate    114,667,091.-   105. A cell or mammal according to any one of the above    configurations, examples, embodiments or aspects, wherein the human    IgH VDJ region comprises nucleotides 105,400,051 to 106,368,585 from    human chromosome 14 (coordinates refer to NCBI36 for the human    genome).-   106. A method, cell or mammal according to any one of the above    configurations, examples, embodiments or aspects, wherein a human    coding region DNA sequence is in a functional arrangement with a    non-human mammal control sequence, such that transcription of the    human DNA is controlled by the non-human mammal control sequence.-   107. A method according to aspect 106 wherein the initiation    cassette is inserted between the mouse J4 and C alpha exons.-   108. An initiation cassette suitable for use in the method of aspect    107 comprising a vector backbone sequence and a selection marker.    -   Inactivation of endogenous antibody chain expression by        insertion of human antibody variable region gene segments-   109. A non-human vertebrate (optionally a mouse or rat) or non-human    vertebrate cell (optionally a mouse or rat cell) having a genome    that    -   (i) comprises a transgenic antibody chain locus capable of        expressing an antibody chain comprising a human variable region        (optionally following antibody gene rearrangement); and    -   (ii) is inactivated for endogenous non-human vertebrate antibody        chain expression; wherein the transgenic locus comprises    -   (iii) a DNA sequence comprising a plurality of human antibody        variable region gene segments inserted between endogenous        antibody variable region gene segments and an endogenous        antibody constant region, whereby endogenous antibody chain        expression is inactivated.    -   The transgenic locus is a heavy chain or light chain locus.    -   Inactivation of endogenous heavy chain expression in non-human        vertebrates such as mice and rats has involved the deletion of        all or part of the endogenous heavy chain VDJ region (including        sequences between gene segments). The ADAM6 genes are present in        the endogenous mouse VDJ region. In mouse, there are two copies        of ADAM6 (ADAM6a, ADAM6b) located between the VH and D gene        segments in the IgH locus of chromosome 12 (in the intervening        region between mouse VH5-1 and D1-1 gene segments). These two        adjacent intronless ADAM6 genes have 95% nucleotide sequence        identity and 90% amino acid identity. In human and rat, there is        only one ADAM6 gene. Expression pattern analysis of mouse ADAM6        shows that it is exclusively expressed in testis [1]. Although        ADAM6 transcripts can be detected in lymphocytes, it is        restricted to the nucleus, suggesting that the transcription of        ADAM6 gene in particular was due to transcriptional read-through        from the D region rather than active messenger RNA production        [2]. In rat, ADAM6 is on chromosome 6.    -   Mature ADAM6 protein is located on the acrosome and the        posterior regions of sperm head. Notably, ADAM6 forms a complex        with ADAM2 and ADAM3, which is required for fertilization in        mice [3]. Reference [4] implicates ADAM6 in a model where this        protein interacts with ADAM3 after ADAM6 is sulphated by TPST2,        sulphation of ADAM6 being critical for stability and/or complex        formation involving ADAM6 and ADAM3, and thus ADAM6 and ADAM3        are lost from Tpst2-null sperm. The study observes that        Tpst2-deficient mice have male infertility, sperm mobility        defects and possible abnormalities in sperm-egg membrane        interactions.    -   Thus, the maintenance of ADAM6 expression in sperm is crucial        for fertility. Thus, it is thought that transgenic male mice and        rats in which ADAM6 genes have been deleted are not viably        fertile. This hampers breeding of colonies and hampers the        utility of such mice as transgenic antibody-generating        platforms. It would be desirable to provide improved non-human        transgenic antibody-generating vertebrates that are fertile.-   [1]. Choi I, et. al., Characterization and comparative genomic    analysis of intronless Adams with testicular gene expression.    Genomics. 2004 April; 83(4):636-46.-   [2]. Featherstone K, Wood A L, Bowen A J, Corcoran A E. The mouse    immunoglobulin heavy chain V-D intergenic sequence contains    insulators that may regulate ordered V(D)J recombination. J Biol    Chem. 2010 Mar. 26; 285(13):9327-38. Epub 2010 Jan. 25.-   [3]. Han C, et. al., Comprehensive analysis of reproductive ADAMs:    relationship of ADAM4 and ADAM6 with an ADAM complex required for    fertilization in mice. Biol Reprod. 2009 May; 80(5):1001-8. Epub    2009 Jan. 7.-   [4]. Marcello et al, Lack of tyrosylprotein sulfotransferase-2    activity results in altered sperm-egg interactions and loss of ADAM3    and ADAM6 in epididymal sperm, J Biol Chem. 2011 Apr. 15;    286(15):13060-70. Epub 2011 Feb. 21.    -   According to aspect 109 of the invention, inactivation does not        involve deletion of the VDJ region or part thereof including        endogenous ADAM6, but instead inactivation by insertion allows        for the preservation of endogenous ADAM6 and thus does not risk        infertility problems.    -   The final mouse resulting from the method (or a mouse derived        from a cell produced by the method) is in one embodiment a male,        so that the invention improves upon the prior art male        transgenic mice that are infertile as a result of genomic        manipulation. Fertile mice produce sperm that can fertilise eggs        from a female mouse. Fertility is readily determined, for        example, by successfully breeding to produce an embryo or child        mouse. In another embodiment, the method of the invention makes        a final female mouse. Such females are, of course, useful for        breeding to create male progeny carrying ADAM6 and which are        fertile.    -   In one embodiment of aspect 109, the genome is homozygous for        the transgenic locus. For example, the genome is homozygous for        endogenous ADAM6 genes.    -   In one embodiment of the vertebrate of aspect 109, the genome is        inactivated for expression of endogenous heavy and kappa (and        optionally also lambda) chains.    -   In one embodiment, in part (iii) of aspect 109 said DNA        comprises human VH, D and JH gene segments or human VL and JL        gene segments (eg, Vκ and Jκ gene segments). In an example, the        DNA comprises a landing pad having a selectable marker, eg, a        HPRT gene, neomycin resistance gene or a puromycin resistance        gene; and/or a promoter.    -   In one embodiment, in part (iii) of aspect 109 the endogenous        gene segments are the entire endogenous VDJ region of a heavy        chain locus and/or the endogenous constant region is a Cmu or        Cgamma.    -   In one embodiment, in part (iii) of aspect 109 the endogenous        gene segments are the entire endogenous VJ region of a kappa        chain locus and/or the endogenous constant region is a Ckappa    -   In one embodiment, in part (iii) of aspect 109 the endogenous        gene segments are the entire endogenous VJ region of a lambda        chain locus and/or the endogenous constant region is a Clambda.    -   The non-human vertebrate cell can be a hybridoma, B-cell, ES        cell or an IPS cell. When the cell is an ES cell or IPS cell,        the endogenous antibody chain expression is inactivated        following differentiation of the cell into a progeny B-cell (eg,        in a B-cell in a non-human vertebrate).    -   The invention further provides:—-   110. The vertebrate or cell according to aspect 109, wherein said    plurality of human antibody gene segments comprises at least 11    human V segments and/or at least 6 human J segments, eg at least 11    human VH gene segments and at least 6 human JH segments and    optionally also at least 27 human D segments; optionally with the    human inter-gene segment intervening sequences. In an embodiment,    the human antibody gene segments are provided by a stretch of DNA    sequence of human chromosome 14, comprising the gene segments and    intervening sequences in germline configuration.-   111. The vertebrate or cell according to aspect 109 or 110, wherein    said inserted DNA sequence comprises a human nucleotide sequence    comprising said antibody gene segments, wherein the nucleotide    sequence is at least 110, 130, 150, 170, 190, 210, 230, 250, 270 or    290 kb. In an embodiment, the nucleotide sequence corresponds to a    stretch of DNA sequence of human chromosome 14, comprising the gene    segments and intervening sequences in germline configuration, eg, at    least a sequence corresponding to the nucleotide sequence from    coordinate 106328951 to coordinate 106601551 of a human chromosome    14, eg, a sequence in the GRCH37/hg19 sequence database.-   112. The vertebrate or cell according to aspect 109, wherein the    transgenic locus is a light chain kappa locus and the human antibody    gene segments are between the 3′-most endogenous Jk gene segment and    endogenous Ck; optionally wherein the human antibody gene segments    comprise five functional human Jλ-Cλ clusters and at least one human    Vλ gene segment, eg, at least a sequence corresponding to the    nucleotide sequence from coordinate 23217291 to 23327884 of a lambda    locus found on a human chromosome 22.-   113. The vertebrate or cell according to any one of aspects 109 to    112, wherein the transgenic locus is a heavy chain locus and the    human antibody gene segments are between the 3′-most endogenous JH    gene segment (eg, JH4 in a mouse genome) and endogenous Cmu.-   114. The vertebrate or cell according to any one of aspects 109 to    113, wherein the genome is homozygous for said transgenic locus.-   115. A mouse or mouse cell or a rat or rat cell according to any one    of aspects 109 to 114.-   116. A method of making a non-human vertebrate cell (optionally a    mouse or rat cell), the method comprising    -   (a) providing a non-human ES cell whose genome comprises an        endogenous antibody chain locus comprising endogenous antibody        variable region gene segments and an endogenous antibody        constant region; and    -   (b) making a transgenic antibody chain locus by inserting into        said endogenous locus a DNA sequences comprising a plurality of        human antibody variable region gene segments between said        endogenous antibody variable region gene segments and said        endogenous constant region, so that the human antibody variable        region gene segments are operably connected upstream of the        endogenous constant region,    -   whereby a non-human vertebrate ES cell is produced that is        capable of giving rise to a progeny cell in which endogenous        antibody expression is inactivated and wherein the progeny is        capable of expressing antibodies comprising human variable        regions; and    -   (c) optionally differentiating said ES cell into said progeny        cell or a non-human vertebrate (eg, mouse or rat) comprising        said progeny cell.-   117. The method according to aspect 116, wherein said plurality of    human antibody gene segments comprises at least 11 human V segments.-   118. The method according to aspect 116 or 117, wherein said    plurality of human antibody gene segments comprises at least 6 human    J segments.-   119. The method according to aspect 116, 117 or 118, wherein a human    nucleotide sequence is inserted in step (b), the nucleotide sequence    comprising said antibody gene segments, wherein the nucleotide    sequence is at least 110 kb.-   120. The method according to any one of aspects 110 to 113, wherein    the endogenous locus is a heavy chain locus and the human antibody    gene segments are between the 3′-most endogenous JH gene segment and    endogenous Cmu.-   121. The method according to any one of aspects 116 to 120, wherein    the progeny cell is homozygous for said transgenic locus.    -   In one embodiment of the method of aspect 116, the method        comprises inactivating the genome for expression of endogenous        heavy and kappa (and optionally also lambda) chains.    -   In one embodiment of the method of aspect 116, in part (b) said        DNA sequence comprises human VH, D and JH gene segments or human        VL and JL gene segments (eg, Vκ and Jκ gene segments). In an        example, the DNA comprises a landing pad having a selectable        marker, eg, a HPRT gene, neomycin resistance gene or a puromycin        resistance gene; and/or a promoter.    -   In one embodiment, in part (b) of aspect 116 the endogenous gene        segments are the entire endogenous VDJ region of a heavy chain        locus and/or the endogenous constant region is a Cmu or Cgamma.    -   In one embodiment, in part (b) of aspect 116 the endogenous gene        segments are the entire endogenous VJ region of a kappa chain        locus and/or the endogenous constant region is a Ckappa    -   In one embodiment, in part (b) of aspect 116 the endogenous gene        segments are the entire endogenous VJ region of a lambda chain        locus and/or the endogenous constant region is a Clambda.    -   The non-human vertebrate cell can be a hybridoma, B-cell, ES        cell or an IPS cell. When the cell is an ES cell or IPS cell,        the endogenous antibody chain expression is inactivated        following differentiation of the cell into a progeny B-cell (eg,        in a B-cell in a non-human vertebrate).

The invention further provides:—

The method according to aspect 116, wherein said inserted DNA sequencecomprises a human nucleotide sequence comprising said human antibodygene segments, wherein the nucleotide sequence is at least 110, 130,150, 170, 190, 210, 230, 250, 270 or 290 kb. In an embodiment, thenucleotide sequence corresponds to a stretch of DNA sequence of humanchromosome 14, comprising the gene segments and intervening sequences ingermline configuration, eg, at least a sequence corresponding to thenucleotide sequence from coordinate 106328951 to coordinate 106601551 ofa human chromosome 14, eg, a sequence in the GRCH37/hg19 sequencedatabase.

The method according to aspect 116, wherein the transgenic locus is alight chain kappa locus and the human antibody gene segments are betweenthe 3′-most endogenous Jk gene segment and endogenous Ck; optionallywherein the human antibody gene segments comprise five functional humanJλ-Cλ clusters and at least one human Vλ gene segment, eg, at least asequence corresponding to the nucleotide sequence from coordinate23217291 to 23327884 of a lambda locus found on a human chromosome 22.

The method according to aspect 116, wherein, wherein the transgeniclocus is a heavy chain locus and the human antibody gene segments areinserted between the 3′-most endogenous JH gene segment (eg, JH4 in amouse genome) and endogenous Cmu.

-   122. The method according to any one of aspects 116 to 121,    comprising making the genome of the progeny homozygous for said    transgenic locus.    -   Isolating antibodies from transgenic non-human vertebrates of        the invention & useful antigen-specific antibodies of        therapeutically-relevant affinities-   123. A method of isolating an antibody that binds a predetermined    antigen, the method comprising    -   (a) providing a vertebrate (optionally a mammal; optionally a        mouse or rat according to any one of the above configurations,        examples, embodiments or aspects;    -   (b) immunising said vertebrate with said antigen (optionally        wherein the antigen is an antigen of an infectious disease        pathogen);    -   (c) removing B lymphocytes from the vertebrate and selecting one        or more B lymphocytes expressing antibodies that bind to the        antigen;    -   (d) optionally immortalising said selected B lymphocytes or        progeny thereof, optionally by producing hybridomas therefrom;        and    -   (e) isolating an antibody (eg, and IgG-type antibody) expressed        by the B lymphocytes.-   124. The method of aspect 123, comprising the step of isolating from    said B lymphocytes nucleic acid encoding said antibody that binds    said antigen; optionally exchanging the heavy chain constant region    nucleotide sequence of the antibody with a nucleotide sequence    encoding a human or humanised heavy chain constant region and    optionally affinity maturing the variable region of said antibody;    and optionally inserting said nucleic acid into an expression vector    and optionally a host.-   125. The method of aspect 123 or 124, further comprising making a    mutant or derivative of the antibody produced by the method of    aspect 122 or 123.    -   As demonstrated by the examples below, the non-human vertebrates        of the invention are able to produce antigen-specific antibodies        of sub-50 nM affinity with human sequences in their CDR3        regions. Thus, the invention further provides:—-   126. An antibody or fragment (eg, a Fab or Fab₂) thereof comprising    variable regions that specifically bind a predetermined antigen with    a sub-50 nM affinity (optionally sub-40, 30, 20, 10, 1, 0.1 or 0.01    nM) as determined by surface plasmon resonance, wherein the antibody    is isolated from a non-human vertebrate (optionally a mammal;    optionally a mouse or rat) according to any one of the above    configurations, examples, embodiments or aspects and comprises heavy    chain CDR3s (as defined by Kabat) encoded by a rearranged VDJ of    said vertebrate, wherein the VDJ is the product of rearrangement in    vivo of a human JH gene segment of a heavy chain locus of said    vertebrate with D (optionally a human D gene segment of said locus)    and VH gene segments.    -   In one embodiment, the surface plasmon resonance (SPR) is        carried out at 25° C. In another embodiment, the SPR is carried        out at 37° C.    -   In one embodiment, the SPR is carried out at physiological pH,        such as about pH7 or at pH7.6 (eg, using Hepes buffered saline        at pH7.6 (also referred to as HBS-EP)).    -   In one embodiment, the SPR is carried out at a physiological        salt level, eg, 150 mM NaCl.    -   In one embodiment, the SPR is carried out at a detergent level        of no greater than 0.05% by volume, eg, in the presence of P20        (polysorbate 20; eg, Tween-20™) at 0.05% and EDTA at 3 mM.    -   In one example, the SPR is carried out at 25° C. or 37° C. in a        buffer at pH7.6, 150 mM NaCl, 0.05% detergent (eg, P20) and 3 mM        EDTA. The buffer can contain 10 mM Hepes. In one example, the        SPR is carried out at 25° C. or 37° C. in HBS-EP. HBS-EP is        available from Teknova Inc (California; catalogue number H8022).    -   In an example, the affinity of the antibody is determined using        SPR by    -   1. Coupling anti-mouse (or other relevant non-human vertebrate)        IgG (eg, Biacore BR-1008-38) to a biosensor chip (eg, GLM chip)        such as by primary amine coupling;    -   2. Exposing the anti-mouse IgG (non-human vertebrate antibody)        to a test IgG antibody to capture test antibody on the chip;    -   3. Passing the test antigen over the chip's capture surface at        1024 nM, 256 nM, 64 nM, 16 nM, 4 nM with a 0 nM (i.e. buffer        alone); and    -   4. And determining the affinity of binding of test antibody to        test antigen using surface plasmon resonance, eg, under an SPR        condition discussed above (eg, at 25° C. in physiological        buffer). SPR can be carried out using any standard SPR        apparatus, such as by Biacore™ or using the ProteOn XPR36™        (Bio-Rad®).

Regeneration of the capture surface can be carried out with 10 mMglycine at pH1.7. This removes the captured antibody and allows thesurface to be used for another interaction. The binding data can befitted to 1:1 model inherent using standard techniques, eg, using amodel inherent to the ProteOn XPR36™ analysis software.

The invention also relates to an scFv, diabody or other antibodyfragment comprising a VH and VL domain from an antibody or fragment ofaspect 126 (optionally following affinity maturation, eg, by phagedisplay).

In one embodiment, the antigen is a serpin, eg, ovalbumin, antithrombinor antitrypsin. Serpins are a group of proteins with similar structuresthat were first identified as a set of proteins able to inhibitproteases. The acronym serpin was originally coined because many serpinsinhibit chymotrypsin-like serine proteases (serine protease inhibitors).The first members of the serpin superfamily to be extensively studiedwere the human plasma proteins antithrombin and antitrypsin, which playkey roles in controlling blood coagulation and inflammation,respectively. Initially, research focused upon their role in humandisease: antithrombin deficiency results in thrombosis and antitrypsindeficiency causes emphysema. In 1980 Hunt and Dayhoff made thesurprising discovery that both these molecules share significant aminoacid sequence similarity to the major protein in chicken egg white,ovalbumin, and they proposed a new protein superfamily.

-   127. An antibody or fragment that is identical to an antibody of    aspect 126 or a derivative thereof (optionally a derivative whose    constant regions are human and/or an affinity matured derivative)    that specifically binds said antigen with a sub-50 nM affinity as    determined by surface plasmon resonance.-   128. A pharmaceutical composition comprising an antibody or fragment    of aspect 126 or 127 and a pharmaceutically-acceptable diluent,    excipient or carrier.-   129. A nucleotide sequence encoding a heavy chain variable region of    an antibody or fragment of aspect 126 or 127, optionally as part of    a vector (eg, an expression vector).-   130. The nucleotide sequence of aspect 129, wherein the sequence is    a cDNA derived from a B-cell of the vertebrate from which the    antibody of aspect 126 is isolated, or is identical to such a cDNA.-   131. An isolated host cell (eg, a hybridoma or a CHO cell or a    HEK293 cell) comprising a nucleotide sequence according to aspect    129 or 130.-   132. A method of isolating an antibody that binds a predetermined    antigen, the method comprising    -   (a) providing a vertebrate (optionally a mammal; optionally a        mouse or rat according to any one of the above configurations,        examples, embodiments or aspects;    -   (b) immunising said vertebrate with said antigen;    -   (c) removing B lymphocytes from the vertebrate and selecting a B        lymphocyte expressing an antibody that binds to the antigen with        sub-nM affinity, wherein the antibody is according to aspect        126;    -   (d) optionally immortalising said selected B lymphocyte or        progeny thereof, optionally by producing hybridomas therefrom;        and    -   (e) isolating an antibody (eg, and IgG-type antibody) expressed        by the B lymphocyte.-   133. The method of aspect 132, comprising the step of isolating from    said B lymphocyte nucleic acid encoding said antibody that binds    said antigen; optionally exchanging the heavy chain constant region    nucleotide sequence of the antibody with a nucleotide sequence    encoding a human or humanised heavy chain constant region and    optionally affinity maturing the variable region of said antibody;    and optionally inserting said nucleic acid into an expression vector    and optionally a host.-   134. The method of aspect 132 or 133, further comprising making a    mutant or derivative of the antibody produced by the method of    aspect 132 or 133.    -   Inactivation by inversion of endogenous VDJ to genome desert        regions-   135. A mouse or mouse cell comprising inverted endogenous heavy    chain gene segments (eg, VH, D and JH, such as the entire endogenous    heavy chain VDJ region) that are immediately 3′ of position    119753123, 119659458 or 120918606 on an endogenous mouse chromosome    12, wherein the mouse comprises a transgenic heavy chain locus    comprising a plurality of human VH gene segments, a plurality of    human D segments and a plurality of human JH segments operably    connected upstream of an endogenous constant region (eg, C mu) so    that the mouse or cell (optionally following differentiation into a    B-cell) is capable of expressing an antibody comprising a variable    region comprising sequences derived from the human gene segments.-   136. The mouse or cell of aspect 135, wherein the genome of the    mouse or cell is homozygous for said chromosome 12.-   137. A cassette for inversion and inactivation of endogenous    non-human vertebrate (eg, mouse or rat) antibody chain gene    segments, the segments being part of an antibody chain locus    sequence on a chromosome of a non-human vertebrate (eg, mouse or    rat) cell (eg, ES cell) wherein the sequence is flanked at its 3′    end by a site-specific recombination site (eg, lox, rox or fit), the    cassette comprising a nucleotide sequence encoding an expressible    label or selectable marker and a compatible site-specific    recombination site (eg, lox, rox or frt) flanked by a 5′ and a 3′    homology arm, wherein the homology arms correspond to or are    homologous to adjacent stretches of sequence in the cell genome on a    different chromosome or on said chromosome at least 10 mb away from    the endogenous gene segments.-   138. A cassette for inversion and inactivation of endogenous mouse    antibody heavy chain gene segments, the segments being part of a    heavy chain locus sequence on chromosome 12 of a mouse cell (eg, ES    cell) wherein the sequence is flanked at its 3′ end by a    site-specific recombination site (eg, lox, rox or fit), the cassette    comprising a nucleotide sequence encoding an expressible label or    selectable marker and a compatible site-specific recombination site    (eg, lox, rox or fit) flanked by a 5′ and a 3′ homology arm,    wherein (i) the 5′ homology arm is mouse chromosome 12 DNA from    coordinate 119753124 to coordinate 119757104 and the 3′ homology arm    is mouse chromosome 12 DNA from coordinate 119749288 to    119753123; (ii) the 5′ homology arm is mouse chromosome 12 DNA from    coordinate 119659459 to coordinate 119663126 and the 3′ homology arm    is mouse chromosome 12 DNA from coordinate 119656536 to 119659458;    or (iii) the 5′ homology arm is mouse chromosome 12 DNA from    coordinate 120918607 to coordinate 120921930 and the 3′ homology arm    is mouse chromosome 12 DNA from coordinate 120915475 to 120918606.-   139. A method of inactivating gene segments of an endogenous    antibody locus, the method comprising    -   (i) Providing a non-human vertebrate cell (eg, an ES cell, eg, a        mouse ES cell) whose genome comprises an antibody chain locus        comprising endogenous variable region gene segments;    -   (ii) Targeting a site-specific recombination site to flank the        3′ of the 3′-most of said endogenous gene segments;    -   (iii) Targeting a second site-specific recombination site at        least 10 mb away from said endogenous gene segments, the second        site being compatible with the first site inverted with respect        to the first site;    -   (iv) Expressing a recombinase compatible with said sites to        effect site-specific recombination between said sites, thereby        inverting and moving said gene segments away from said locus,        wherein the endogenous gene segments are inactivated; and    -   (v) Optionally developing the cell into a progeny cell or        vertebrate (eg, mouse or rat) whose genome is homozygous for the        inversion.-   140. A mouse or mouse cell whose genome comprises an inversion of a    chromosome 12, wherein the inversion comprises inverted endogenous    heavy chain gene segments (eg, VH, D and JH, such as the entire    endogenous heavy chain VDJ region); wherein the mouse comprises a    transgenic heavy chain locus comprising a plurality of human VH gene    segments, a plurality of human D segments and a plurality of human    JH segments operably connected upstream of an endogenous constant    region (eg, C mu) so that the mouse or cell (optionally following    differentiation into a B-cell) is capable of expressing an antibody    comprising a variable region comprising sequences derived from the    human gene segments; and wherein the inversion is (i) an inversion    of mouse chromosome 12 from coordinate 119753123 to coordinate    114666436; (ii) an inversion of mouse chromosome 12 from coordinate    119659458 to coordinate 114666436; or (iii) an inversion of mouse    chromosome 12 from coordinate 12091806 to coordinate 114666436.

Other aspects include:

A method for producing an antibody specific to a desired antigen themethod comprising immunizing a non-human mammal as disclosed herein withthe desired antigen and recovering the antibody or a cell producing theantibody.

A method for producing a fully humanised antibody comprising immunizinga non-human mammal as disclosed herein and then replacing the non-humanmammal constant region of an antibody specifically reactive with theantigen with a human constant region, suitably by engineering of thenucleic acid encoding the antibody.

A method, cell or mammal as disclosed herein wherein a human codingregion DNA sequence is in a functional arrangement with a non-humanmammal control sequence, such that transcription of the DNA iscontrolled by the non-human mammal control sequence. In one aspect thehuman coding region V, D or J region is in a functional arrangement witha mouse promoter sequence.

The invention also relates to a humanised antibody produced according toany methods disclosed herein and use of a humanised antibody so producedin medicine.

Endogenous Light Chain Inactivation & High Expression of Human LambdaVariable Regions in Transgenic Non-Human Vertebrates & Cells

As explained further in the examples below, the inventors havesurprisingly observed very high expression levels of light chainscomprising human lambda variable regions (at least 80% human V lambda)from transgenic light chain loci produced by targeted insertion of humanlambda gene segments into endogenous non-human vertebrate light chainloci. This is possible even in the presence of endogenous non-humanvertebrate V and J gene segments in the vertebrate genome. Also, thesurprisingly high levels of expression are achieved when insertion ofhuman lambda gene segments are in the endogenous kappa or lambda locus.Such high levels by targeted insertion has not hitherto been publishedin the art.

The inventors also surprisingly observed that endogenous kappa chainexpression can be completely inactivated by targeted insertion of humanlambda gene sequence into the endogenous kappa locus, as explainedfurther in the examples.

The targeted insertion of human gene segments into endogenous Ig loci isadvantageous because it enables the operable location of inserted humanIg sequences with respect to endogenous Ig constant regions andendogenous control regions, such as enhancers and other locus controlregions for example. Thus, targeted insertion allows one to harnessendogenous control important in one or more of Ig gene segmentrecombination, allelic exclusion, affinity maturation, class switching,levels of Ig expression and desirable development of the B-cellcompartment. As such, targeted insertion is superior to early attemptsin the art to produce transgenic Ig loci and expression, which attemptsrelied on the introduction into non-human vertebrate cells of vectorssuch as YACs bearing human Ig gene segments. YACs are randomlyintegrated into the vertebrate cell genome, so that it is difficult toachieve the control provided by targeted insertion and the concomitantbenefits that are brought in terms of harnessing endogenous controlmechanisms. In addition, random insertion often results in the insertedhuman Ig gene segments coming under the control of heterologous controlelements and/or epigenetic chromosomal modifications such as methylationand chromatin confirmations, either of which can be detrimental toproper Ig gene segment recombination, allelic exclusion, affinitymaturation, class switching, levels of Ig expression and desirabledevelopment of the B-cell compartment. Random insertion typicallyresults in 2 or more copies of the introduced transgene which can causechromosomal instability and therefore result in poor breedingperformance of the animals in addition to detrimental effects on properIg gene segment recombination, allelic exclusion, affinity maturation,class switching, levels of Ig expression and desirable development ofthe B-cell compartment. Thus, prior art attempts using random insertionhave tended to lead to poor B-cell development, relatively small B-cellcompartments and inferior Ig expression and a concomitant difficulty inisolating an antibody with a desired characteristic.

The invention therefore provides the following aspects:—

-   -   ≥80% human lambda variable regions

-   1. A non-human vertebrate (eg, a mouse or rat) whose genome    comprises an Ig gene segment repertoire produced by targeted    insertion of human Ig gene segments into one or more endogenous Ig    loci, the genome comprising human Vλ and Jλ gene segments upstream    of a constant region, wherein the human Vλ and Jλ gene segments have    been provided by insertion into an endogenous light chain locus of    the vertebrate, wherein the vertebrate expresses immunoglobulin    light chains comprising lambda variable regions (lambda light    chains), and wherein at least 80% of the variable regions of the    lambda light chains expressed by the vertebrate are derived from    recombination of human Vλ and Jλ gene segments. This is demonstrated    in the examples below.

For example, at least 70, 75, 80, 84, 85, 90, 95, 96, 97, 98 or 99%, or100% of the variable regions of the lambda light chains expressed by thevertebrate are derived from recombination of human Vλ and Jλ genesegments. This is demonstrated in the examples below.

In one embodiment, there is provided a non-human vertebrate ES cell (eg,a mouse ES cell or rat ES cell) whose genome comprises an Ig genesegment repertoire produced by targeted insertion of human Ig genesegments into one or more endogenous Ig loci, the genome comprisinghuman Vλ and Jλ gene segments upstream of a constant region, wherein thehuman Vλ and Jλ gene segments have been provided by insertion into anendogenous light chain locus of the vertebrate cell, wherein the cellcan develop into a vertebrate that expresses immunoglobulin light chainscomprising lambda variable regions (lambda light chains), and wherein atleast 80% (for example, at least 70, 75, 80, 84, 85, 90, 95, 96, 97, 98or 99%, or 100%) of the variable regions of the lambda light chainsexpressed by the vertebrate are derived from recombination of human Vλand Jλ gene segments.

-   2. The vertebrate or cell of aspect 1, optionally wherein the human    Vλ and Jλ insertion comprises at least the functional human V and J    gene segments (optionally also human Cλ) comprised by a human lambda    chain Ig locus from Vλ2-18 to Cλ7. In one example, the insertion    also comprises lambda inter-gene segment sequences. These are human    sequences or they can be sequences of the non-human vertebrate    species (eg, where the vertebrate is a mouse, sequences between    corresponding mouse lambda gene segments can be used).-   3. The vertebrate or cell of aspect 1 or 2, optionally wherein the    genome is homozygous for the human Vλ and Jλ gene segment insertion    and endogenous kappa chain expression in said vertebrate is    substantially or completely inactive. In one example, less than 10,    5, 4, 3, 2, 1 or 0.5% of light chains are provided by endogenous    kappa chains (ie, kappa chains whose variable regions are derived    from recombination of non-human vertebrate V and J gene segments).-   4. The vertebrate or cell of any preceding aspect, optionally    wherein the endogenous locus is an endogenous kappa locus.-   5. The vertebrate or cell of any preceding aspect, optionally    wherein the endogenous locus is an endogenous lambda locus.

≥60% of all light chains have human lambda V regions

-   6. A non-human vertebrate (eg, a mouse or rat) whose genome    comprises an Ig gene segment repertoire produced by targeted    insertion of human Ig gene segments into one or more endogenous Ig    loci, the genome comprising (i) human Vλ and Jλ gene segments    upstream of a constant region, wherein the human Vλ and Jλ gene    segments have been provided by insertion into an endogenous light    chain locus of the vertebrate and (ii) kappa V gene segments    upstream of a constant region, wherein the vertebrate expresses    immunoglobulin light chains comprising human lambda variable regions    (human lambda light chains), and wherein at least 60% of the light    chains expressed by the vertebrate are provided by said human lambda    light chains. This is demonstrated in the examples below.

For example, at least 65, 70, 75, 80, 84, 85, 90, 95, 96, 97, 98 or 99%,or 100% of the light chains expressed by the vertebrate are provided bysaid human lambda light chains. For example, at least 84% of the lightchains expressed by the vertebrate are provided by said human lambdalight chains. For example, at least 95% of the light chains expressed bythe vertebrate are provided by said human lambda light chains. This isdemonstrated in the examples below.

In one embodiment, there is provided a non-human vertebrate ES cell (eg,a mouse ES cell or rat ES cell) whose genome comprises an Ig genesegment repertoire produced by targeted insertion of human Ig genesegments into one or more endogenous Ig loci, the genome comprising (i)human Vλ and Jλ gene segments upstream of a constant region, wherein thehuman Vλ and Jλ gene segments have been provided by insertion into anendogenous light chain locus of the vertebrate and (ii) kappa V genesegments upstream of a constant region, wherein the cell can developinto a vertebrate that expresses immunoglobulin light chains comprisinghuman lambda variable regions (human lambda light chains), and whereinat least 60% of the light chains expressed by the vertebrate areprovided by said human lambda light chains.

-   7. A non-human vertebrate or a non-human vertebrate cell (eg, a    mouse, rat, mouse cell or a rat cell) whose genome comprises an Ig    gene segment repertoire produced by targeted insertion of human Ig    gene segments into one or more endogenous Ig loci, the genome    comprising a targeted insertion of human immunoglobulin Vλ and Jλ    gene segments into an endogenous non-human vertebrate light kappa or    lambda chain locus downstream of endogenous VL and JL gene segments    for expression of a light chains comprising human lambda variable    regions; wherein the human Vλ and Jλ insertion comprises at least    the functional human V and J (and optionally also functional human    Cλ) gene segments comprised by a human lambda chain Ig locus from    Vλ2-18 to Cλ7.

As demonstrated in the examples, endogenous light chain expression fromsaid locus is inactivated and also human lambda variable regionexpression dominates over endogenous lambda variable region expression.

By “downstream” is meant 3′ of the gene segments on the same chromosome.In one example, the endogenous V and J gene segments are inverted withrespect to the human gene segments and optionally moved out of theendogenous light chain locus. In one example, the human gene segmentsare downstream of all of the endogenous V and J segments of said kappaor lambda locus. The possibility of retaining the endogenous V-Jsequences and intergenic sequences is advantageous since embeddedcontrol regions and/or genes are retained that may be desirable in thevertebrate.

Optionally the insertion also comprises lambda inter-gene segmentsequences. These are human sequences or they can be sequences of thenon-human vertebrate species (eg, where the vertebrate is a mouse,sequences between corresponding mouse lambda gene segments can be used).

Expression of VJCλ Lambda Chains

-   8. A non-human vertebrate or a non-human vertebrate cell (eg, a    mouse, rat, mouse cell or a rat cell) whose genome comprises an Ig    gene segment repertoire produced by targeted insertion of human Ig    gene segments into one or more endogenous Ig loci, the genome    comprising a targeted insertion of human immunoglobulin Vλ, Jλ and    Cλ genes into an endogenous non-human vertebrate kappa or lambda    light chain locus upstream of an endogenous non-human vertebrate    kappa or lambda constant region for expression of a human VJC light    chain; optionally wherein the human VJC insertion comprises at least    the functional human V, J and C gene segments comprised by a human    lambda chain Ig locus from Vλ3-1 to Cλ7 (eg, comprised by a human    lambda chain Ig locus from 2-18 to Cλ7).

As demonstrated in the examples, human lambda variable region expressiondominates over endogenous kappa variable region expression. Endogenouskappa chain expression from the endogenous locus can be inactivated.

Optionally the insertion also comprises lambda inter-gene segmentsequences. These are human sequences or they can be sequences of thenon-human vertebrate species (eg, where the vertebrate is a mouse,sequences between corresponding mouse lambda gene segments can be used).

-   9. A non-human vertebrate or a non-human vertebrate cell (eg, a    mouse, rat, mouse cell or a rat cell) whose genome comprises an Ig    gene segment repertoire produced by targeted insertion of human Ig    gene segments into one or more endogenous Ig loci, the genome    comprising a targeted insertion of at least the functional human Vλ    and Jλ (and optionally human functional Cλ) gene segments comprised    by a human lambda chain Ig locus from Vλ3-1 to Cλ7 (optionally from    Vλ2-18 to Cλ7) into an endogenous non-human vertebrate kappa light    chain locus downstream of the mouse Vκ and Jκ gene segments for    expression of a light chain comprising a human lambda variable    region, whereby in the presence of said insertion expression of    endogenous kappa light chains derived from said mouse Vκ and Jκ gene    segments is substantially or completely inactivated.

In one example, less than 10, 5, 4, 3, 2, 1 or 0.5% of light chains areprovided by endogenous kappa chains (ie, kappa chains whose variableregions are derived from recombination of non-human vertebrate Vκ and Jκgene segments).

Optionally the insertion also comprises lambda inter-gene segmentsequences. These are human sequences or they can be sequences of thenon-human vertebrate species (eg, where the vertebrate is a mouse,sequences between corresponding mouse lambda gene segments can be used).

-   10. A non-human vertebrate or a non-human vertebrate cell (eg, a    mouse, rat, mouse cell or a rat cell), wherein in the genome of    which the mouse IgK-VJ has been moved away from the mouse Eκ    enhancer, thereby inactivating endogenous IgK-VJ regions. This is    demonstrated in the examples.-   11. The vertebrate of cell of aspect 10, optionally wherein the    IgK-VJ has been moved away from the mouse Eκ enhancer by insertion    of human VL and JL gene segments between the mouse IgK-VJ and the Eκ    enhancer; optionally wherein the insertion is an insertion as    recited in any preceding aspect 1-9 or an insertion of human Vκ and    Jκ gene segments.-   12. The vertebrate or cell of any preceding aspect, optionally    wherein the human Vλ and Jλ gene segments have been inserted within    100, 75, 50, 40, 30, 20, 15, 10 or 5 kb of an endogenous non-human    vertebrate light chain enhancer. In one example, the enhancer is a    lambda enhancer (eg, mouse Eλ2-4, Eλ4-10 or Eλ3-1) when the    insertion is into an endogenous lambda locus. In one example, the    enhancer is a kappa enhancer (eg, iEκ or 3′Eκ) when the insertion is    into an endogenous kappa locus.-   13. The vertebrate or cell of any preceding aspect, optionally    wherein the human Vλ and Jλ gene segments are provided in the genome    by the targeted insertion of at least 10 human Vλ gene segments with    human Jλ gene segments upstream of an endogenous non-human    vertebrate light chain constant region of said light chain locus.    For example, the human gene segments are provided by insertion of at    least a portion of a human Ig lambda chain locus from Vλ2-18 to    Vλ3-1; or at least a portion of a human Ig lambda chain locus from    Vλ2-18 to Vλ3-1 inserted with Jλ1, Jλ2, Jλ3, Jλ6 and Jλ7; or at    least a portion of a human Ig lambda chain locus from Vλ2-18 to Cλ7    (optionally excluding Jλ4Cλ4 and/or Jλ5Cλ5).

Optionally at least 2, 3, 4 or 5 human Jλ are inserted. In oneembodiment, the inserted Jλs are different from each other. For example,human Jλ1, Jλ2, Jλ3, Jλ6 and Jλ7 are inserted, optionally as part ofrespective human JλCλ clusters.

Optionally a human light chain enhancer, eg Eλ, is inserted. Forexample, insertion of human Eλ between the human Jλ segments and theendogenous constant region; or between human Cλ gene segments (whenthese are inserted) and the endogenous constant region.

-   14. The vertebrate or cell of any preceding aspect, optionally    wherein the lambda light chains provide a repertoire of human lambda    variable regions derived from human Vλ gene segments Vλ3-1 and    optionally one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11,    Vλ3-10, Vλ3-9, Vλ2-8 and Vλ4-3 that have been provided in the genome    by targeted insertion into said light chain locus.

This is useful because Vλ3-1 is a highly-used lambda gene segment inhumans (FIG. 59; Ignatovich et al 1997) and thus it is desirable thatcells and vertebrates of the invention provide for the inclusion oflambda variable regions based on this gene segment for selection againstantigen, particularly for the development of antibody therapeutics forhuman use.

-   15. The vertebrate or cell of any preceding aspect, optionally    wherein the lambda light chains provide a repertoire of human lambda    variable regions derived from human Vλ gene segments Vλ2-14 and one    or more of Vλ2-18, Vλ3-16, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8,    Vλ4-3 and Vλ3-1 that have been provided in the genome by targeted    insertion into said light chain locus.

This is useful because Vλ2-14 is a highly-used lambda gene segment inhumans and thus it is desirable that cells and vertebrates of theinvention provide for the inclusion of lambda variable regions based onthis gene segment for selection against antigen, particularly for thedevelopment of antibody therapeutics for human use.

The vertebrate or cell of any preceding aspect, optionally wherein thelambda light chains provide a repertoire of human lambda variableregions derived from human Vλ gene segments Vλ2-8 and one or more ofVλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3 andVλ3-1 that have been provided in the genome by targeted insertion intosaid light chain locus.

This is useful because Vλ2-8 is a highly-used lambda gene segment inhumans and thus it is desirable that cells and vertebrates of theinvention provide for the inclusion of lambda variable regions based onthis gene segment for selection against antigen, particularly for thedevelopment of antibody therapeutics for human use.

The vertebrate or cell of any preceding aspect, optionally wherein thelambda light chains provide a repertoire of human lambda variableregions derived from human Vλ gene segments Vλ3-10 and one or more ofVλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11, Vλ2-14, Vλ3-9, Vλ2-8, Vλ4-3 andVλ3-1 that have been provided in the genome by targeted insertion intosaid light chain locus.

This is useful because Vλ3-10 is a highly-used lambda gene segment inhumans and thus it is desirable that cells and vertebrates of theinvention provide for the inclusion of lambda variable regions based onthis gene segment for selection against antigen, particularly for thedevelopment of antibody therapeutics for human use.

-   16. The vertebrate or cell of any preceding aspect, optionally    wherein the human Vλ gene segments comprise the functional Vλ    comprised by a human lambda chain Ig locus from Vλ2-18 to Vλ3-1.

For example, the human Vλ gene segments comprise at least human V genesegment Vλ3-1 or at least segments Vλ2-18, Vλ3-16, V2-14, Vλ3-12,Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3 and Vλ3-1.

-   17. The vertebrate of any preceding aspect, optionally wherein the    vertebrate expresses more lambda chains than kappa chains. Lambda    chains comprise variable regions derived from recombination of Vλ    and Jλ gene segments—for example, expressed with a lambda constant    region. Kappa chains comprise variable regions derived from    recombination of Vκ and Jκ gene segments—for example, expressed with    a kappa constant region.-   18. The vertebrate of any preceding aspect, optionally wherein the    vertebrate expresses no endogenous kappa chains. For example,    endogenous kappa chain expression can be inactivated by any of the    means described herein, such as by inversion of all or part of the    endogenous kappa VJ region or by insertion of a marker (eg, neo) or    other interfering sequence in an endogenous kappa locus (a locus not    comprising human lambda gene segments according to the invention).-   19. The vertebrate of any preceding aspect, optionally wherein kappa    chain expression is substantially or completely inactive in said    vertebrate. In one example, less than 10, 5, 4, 3, 2, 1 or 0.5% of    light chains are provided by kappa chains.-   20. The vertebrate or cell of any preceding aspect, optionally    wherein a human Eλ enhancer is inserted in said endogenous non-human    vertebrate locus. For example, there is inserted a human 5′ MAR and    human Eλ (and optionally the human 3′ MAR) in germline    configuration. For example, there is inserted a sequence    corresponding to the human lambda intronic region immediately 3′ of    human Jλ7-Cλ7 to, and including, at least the human Eλ (and    optionally also the human 3′ MAR)—optionally including at least 30    kb of intronic region 3′ of the human Eλ.-   21. The vertebrate or cell of any preceding aspect, wherein    optionally at least human JC gene segments Jλ1-Cλ1, Jλ2-Cλ2,    Jλ3-Cλ3, Jλ6-Cλ6 and Jλ7-Cλ7 are inserted in addition to the other    human gene segments.-   22. The vertebrate or cell of any preceding aspect, wherein    optionally the inserted human gene segments are in germline    configuration; optionally with the human inter-gene segment    sequences or the corresponding endogenous non-human vertebrate    inter-gene segment sequences.-   23. The vertebrate or cell of any preceding aspect, wherein    optionally an endogenous non-human vertebrate light chain enhancer    is maintained in the endogenous locus; optionally in germline    configuration. For example, when the endogenous locus is a kappa    locus, an endogenous kappa enhancer is maintained. This can be the    iEk and/or the 3′Ek, optionally in germline configuration with    respect to an endogenous light chain constant region. This may be    useful to help control of light chain expression in the non-human    vertebrate or cell.-   24. The vertebrate or cell of any preceding aspect, optionally    wherein the genome is heterozygous for the human lambda insertion at    the endogenous locus. For example, heterozygous for the human VJ or    VJC insertion at an endogenous kappa (eg, mouse or rat kappa) locus.    This aids and simplifies breeding of the vertebrates since the other    endogenous locus (eg, the other kappa locus) can be used to provide    a different transgenic Ig locus, such as a transgenic kappa locus    comprising human kappa V and J gene segments either upstream of the    endogenous mouse kappa constant region or upstream of a human kappa    constant region. In this case, the kappa enhancers (iEk and/or the    3′Ek) can be maintained in that kappa locus to aid expression in the    vertebrate by using endogenous control mechanisms.

In another embodiment, there is provided a non-human vertebrate or cellaccording to any preceding aspect, wherein

(a) the endogenous locus is an endogenous lambda locus (eg, in a mouse),the genome being heterozygous for the insertion at the lambda locus,thus one allele of the lambda locus comprising the human Vλ and Jλ genesegment insertion (optionally with the human Cλ gene segment insertion;optionally with the human Eλ insertion) as described above;

(b) the other endogenous lambda allele comprises a plurality of human Vκgene segments and one or more human Jκ gene segments upstream of aconstant region (eg, a kappa constant region of said non-humanvertebrate species; a human kappa constant region; the endogenous lambdaconstant region; or a human lambda constant region); optionally with oneor more kappa enhancers (eg, iEk and/or the 3′Ek, eg, of said non-humanvertebrate species); and

(c) endogenous lambda and kappa chain expression has been inactivated.

Thus, there is no expression of light chains comprising variable regionsderived from recombination of endogenous V and J regions, but there isexpression of human lambda and human kappa light chains from the allelesat the endogenous lambda locus. This is beneficial, since the designgreatly aids construction and breeding of vertebrates by avoiding needto provide transgenic loci at both the endogenous lambda and kappa loci.The endogenous kappa locus (and thus endogenous kappa chain expression)can be inactivated by inversion, deletion of kappa gene segments (eg,endogenous V and/or J and/or C kappa) and/or by insertion of aninterrupting sequence such as a marker (eg, neo) into the endogenouskappa locus.

The human kappa segment insertion into the endogenous lambda can becarried out, for example, by inserting a sequence corresponding to aportion of a human kappa locus comprising in germline configuration allfunctional human Vκ and Jκ (ie, optionally excluding pseudogenes andORFs; see the IMGT database); and optionally also a human iEκ.

-   25. The vertebrate or cell of aspect 24, optionally wherein the    genome comprises said human lambda gene segment insertion at one    endogenous non-human vertebrate kappa locus allele, and wherein the    other endogenous kappa locus allele comprises an insertion of human    kappa immunoglobulin V and J genes upstream of an endogenous    non-human vertebrate kappa constant region; optionally wherein an    endogenous kappa light chain enhancer is maintained in one or both    kappa locus; optionally in germline configuration. The vertebrate or    cell of aspect 24, optionally wherein the genome comprises said    human lambda gene segment insertion at one endogenous non-human    vertebrate lambda locus allele, and wherein the other endogenous    lambda locus allele comprises an insertion of human kappa    immunoglobulin V and J genes upstream of an endogenous non-human    vertebrate kappa constant region; optionally wherein an endogenous    lambda light chain enhancer is maintained in one or both lambda    locus; optionally in germline configuration.-   26. The vertebrate or cell of aspect 24, optionally wherein the    genome comprises said human lambda gene segment insertion at one    endogenous non-human vertebrate lambda locus allele, and wherein the    other endogenous lambda locus allele comprises an insertion of human    kappa immunoglobulin V and J genes upstream of an endogenous    non-human vertebrate kappa constant region; optionally wherein an    endogenous lambda light chain enhancer is maintained in one or both    kappa locus; optionally in germline configuration.-   27. The vertebrate or cell of any one of aspects 1 to 23, optionally    wherein the genome is homozygous for the human lambda insertion at    the endogenous non-human vertebrate locus.-   28. The vertebrate or cell of any one of aspects 1 to 23, optionally    wherein the genome is homozygous for a human lambda gene segment    insertion at the endogenous non-human vertebrate kappa and lambda    loci.-   29. The vertebrate or cell of any one of aspects 1 to 23 and 28,    optionally wherein the genome is homozygous for a human lambda gene    segment insertion at the endogenous non-human vertebrate lambda    loci, one endogenous kappa locus allele comprising a human lambda    gene segment insertion and the other endogenous kappa locus allele    comprising an insertion of a plurality of human Vκ and Jκ gene    segments upstream of a Cκ region for the expression of kappa light    chains comprising human kappa variable regions. Human kappa variable    regions are those derived from the recombination of human Vκ and Jκ.-   30. The vertebrate or cell of aspect 27 or 28, optionally wherein    the human lambda gene segment insertions at the kappa and lambda    loci are insertions of the same repertoire of human lambda gene    segments.-   31. The vertebrate or cell of aspect 27 or 28, optionally wherein    the human lambda gene segment insertions at the kappa loci are    different from the human lambda gene segment insertions at the    lambda loci. This is useful for expanding the potential repertoire    of variable regions for subsequent selection against antigen.-   32. A non-human vertebrate or a non-human vertebrate cell (eg, a    mouse, rat, mouse cell or a rat cell) whose genome comprises an Ig    gene segment repertoire produced by targeted insertion of human Ig    gene segments into one or more endogenous Ig loci, the genome    comprising the following light chain loci arrangement

(a) L at one endogenous kappa chain allele and K at the other endogenouskappa chain allele; or

(b) L at one endogenous lambda chain allele and K at the otherendogenous lambda chain allele; or

(c) L at both endogenous kappa chain alleles;

(d) L at both endogenous lambda chain alleles;

(e) L at one endogenous kappa chain allele and the other endogenouskappa chain allele has been inactivated; or

(f) L at one endogenous lambda chain allele and the other endogenouslambda chain allele has been inactivated;

Wherein

L represents a human lambda gene segment insertion of at least thefunctional human Vλ and Jλ (optionally also Cλ gene segments) comprisedby a human lambda chain Ig locus from Vλ3-1 to Cλ7 (eg, comprised by ahuman lambda chain Ig locus from 2-18 to Cλ7); and

K represents a human Vκ and Jκ insertion;

Wherein in the genome the human gene segments are inserted upstream of aconstant region for expression of light chains comprising variableregions derived from the recombination of human V and J gene segments.

-   33. The vertebrate or cell according to aspect 32, optionally    wherein the genome comprises arrangement

(a) and L at one or both endogenous lambda chain alleles; or

(a) and K at one or both endogenous lambda chain alleles; or

(a) and L at one endogenous lambda chain allele and K at the otherendogenous lambda chain allele; or

(b) and L at one or both endogenous kappa chain alleles; or

(b) and K at one or both endogenous kappa chain alleles; or

(b) and L at one endogenous kappa chain allele and K at the otherendogenous kappa chain allele; or

(c) and K at one or both endogenous lambda chain alleles; or

(c) and L at one or both endogenous lambda chain alleles; or

(c) and L at one endogenous lambda chain allele and K at the otherendogenous lambda chain allele; or

(c) and both endogenous lambda chain alleles have been inactivated; or

(d) and L at one or both endogenous kappa chain alleles; or

(d) and K at one or both endogenous kappa chain alleles; or

(d) and L at one endogenous kappa chain allele and K at the otherendogenous kappa chain allele; or

(d) and both endogenous kappa chain alleles have been inactivated.

-   34. The vertebrate or cell of aspect 32 or 33, optionally wherein    endogenous kappa chain expression is substantially or completely    inactivated. Endogenous kappa chains are kappa light chains    comprising variable regions derived from the recombination of    endogenous (non-human vertebrate) Vκ and Jκ gene segments.-   35. The vertebrate or cell of aspect 32, 33 or 34, optionally    wherein endogenous lambda chain expression is substantially or    completely inactive. Endogenous lambda chains are lambda light    chains comprising variable regions derived from the recombination of    endogenous (non-human vertebrate) Vλ and Jλ gene segments.-   36. The vertebrate or cell of any one of aspects 32 to 35,    optionally wherein each L insertion is upstream of an endogenous    lambda or kappa constant region.-   37. The vertebrate or cell of any one of aspects 32 to 36,    optionally wherein each L insertion into a lambda locus is upstream    of an endogenous lambda constant region.-   38. The vertebrate or cell of any one of aspects 32 to 36,    optionally wherein each L insertion into a kappa locus is upstream    of an endogenous kappa constant region.-   39. The vertebrate or cell of any one of aspects 32 to 35,    optionally wherein each L insertion into a lambda locus is upstream    of a human lambda constant region.-   40. The vertebrate or cell of any one of aspects 32 to 35,    optionally wherein each L insertion into a kappa locus is upstream    of a human kappa constant region.-   41. The vertebrate or cell of any one of aspects 32 to 40,    optionally wherein each K insertion is upstream of an endogenous    lambda or kappa constant region.-   42. The vertebrate or cell of any one of aspects 32 to 41,    optionally wherein each K insertion into a lambda locus is upstream    of an endogenous lambda constant region.-   43. The vertebrate or cell of any one of aspects 32 to 42,    optionally wherein each K insertion into a kappa locus is upstream    of an endogenous kappa constant region.-   44. The vertebrate or cell of any one of aspects 32 to 40,    optionally wherein each K insertion into a lambda locus is upstream    of a human lambda constant region.-   45. The vertebrate or cell of any one of aspects 32 to 40 and 44,    optionally wherein each K insertion into a kappa locus is upstream    of a human kappa constant region.-   46. The vertebrate or cell of any one of aspects 32 to 45,    optionally wherein the insertions are according to any one of    aspects 1 to 9, 11 to 16 and 20 to 31.-   47. The vertebrate or cell of any one of aspects 32 to 46,    optionally wherein each human lambda insertion is according to any    one of aspects 1 to 9, 11 to 16 and 20 to 31.-   48. The vertebrate or cell of any one of aspects 32 to 47,    optionally wherein each human kappa insertion is according to any    one of aspects 1 to 9, 11 to 16 and 20 to 31.-   49. The vertebrate or cell of any one of aspects 32 to 48,    optionally wherein each human lambda insertion comprises the    repertoire of human Vλ and Jλ (and optionally Cλ) gene segments.-   50. The vertebrate or cell of any one of aspects 32 to 48,    optionally wherein first and second (and optionally third) human    lambda insertions are made and the insertions comprise different    repertoires of human Vλ and Jλ (and optionally Cλ) gene segments.-   51. The vertebrate or cell of any one of aspects 32 to 50,    optionally wherein each human kappa insertion comprises the    repertoire of human Vκ and Jκ (and optionally Cκ) gene segments.-   52. The vertebrate or cell of any one of aspects 32 to 50,    optionally wherein first and second (and optionally third) human    kappa insertions are made and the insertions comprise different    repertoires of human Vκ and Jκ (and optionally Cκ) gene segments.-   53. The vertebrate or cell of any preceding aspect, optionally    wherein the genome comprises an immunoglobulin heavy chain locus    comprising human VH gene segments, eg, a heavy chain locus as herein    described which comprises human V, D and J gene segments.-   54. A method for producing an antibody or light chain comprising a    lambda variable region specific to a desired antigen, the method    comprising immunizing a vertebrate according to any preceding aspect    with the desired antigen and recovering the antibody or light chain    or recovering a cell producing the antibody or light chain.-   55. A method for producing a fully humanised antibody or antibody    light chain comprising carrying out the method of aspect 54 to    obtain an antibody or light chain comprising a lambda chain    non-human vertebrate constant region, and replacing the non-human    vertebrate constant region with a human constant region, optionally    by engineering of the nucleic acid encoding the antibody or light    chain.-   56. A humanised antibody or antibody light chain produced according    to aspect 54 or a derivative thereof; optionally for use in    medicine.-   57. Use of a humanised antibody or chain produced according to    aspect 54 or a derivative thereof in medicine.-   58. A method of inactivating endogenous Ig-VJ regions in the genome    of a non-human vertebrate or a non-human vertebrate cell (eg, a    mouse, rat, mouse cell or a rat cell), wherein the method comprises    inserting human immunoglobulin gene segments (eg, V and J gene    segments) in the genome between the endogenous Ig-VJ and an    endogenous enhancer or endogenous constant region to move the    endogenous Ig-VJ away from the enhancer or constant region, thereby    inactivating endogenous Ig-VJ regions.

In one embodiment, the endogenous Ig-VJ are heavy chain gene segments,the enhancer is an endogenous heavy chain enhancer, the constant regionis an endogenous heavy chain constant region and the human Ig genesegments comprise human VH, DH and JH gene segments.

In one embodiment, the endogenous Ig-VJ are lambda light chain genesegments, the enhancer is an endogenous lambda chain enhancer, theconstant region is an endogenous lambda chain constant region and thehuman Ig gene segments comprise human Vλ and Jλ gene segments.

In one embodiment, the endogenous Ig-VJ are kappa light chain genesegments, the enhancer is an endogenous kappa chain enhancer, theconstant region is an endogenous kappa chain constant region and thehuman Ig gene segments comprise human Vκ and Jκ gene segments.

A method of inactivating endogenous IgK-VJ regions in the genome of anon-human vertebrate or a non-human vertebrate cell (eg, a mouse, rat,mouse cell or a rat cell), wherein the method comprises inserting humanimmunoglobulin gene segments in the genome between the endogenous IgK-VJand Eκ enhancer to move the IgK-VJ away from the Eκ enhancer, therebyinactivating endogenous IgK-VJ regions.

-   59. The method of aspect 58, wherein optionally the human gene    segments comprise human VL and JL gene segments; optionally wherein    the insertion is an insertion as recited in any one of aspects 1 to    9, 11 to 16 and 20 to 31 or an insertion of human Vκ and Jκ gene    segments.-   60. A method of expressing immunoglobulin light chains in a    non-human vertebrate (eg, a mouse or rat), the light chains    comprising lambda variable regions (lambda light chains), wherein at    least 80% (for example, at least 70, 75, 80, 84, 85, 90, 95, 96, 97,    98 or 99%) of the variable regions of the lambda light chains    expressed by the vertebrate are derived from recombination of human    Vλ and Jλ gene segments, the method comprising providing in the    genome of the vertebrate an Ig gene segment repertoire produced by    targeted insertion of human Ig gene segments into one or more    endogenous Ig loci, the genome comprising human Vλ and Jλ gene    segments upstream of a constant region, wherein the method comprises    inserting at least the functional human Vλ and Jλ (optionally also    human Cλ) gene segments (and optionally inter-gene segment    sequences) comprised by a human lambda chain Ig locus from Vλ2-18 to    Cλ7 into an endogenous light chain locus of the vertebrate, wherein    at least 80% (for example, at least 70, 75, 80, 84, 85, 90, 95, 96,    97, 98 or 99%) of the variable regions of the lambda light chains    expressed by the vertebrate are derived from recombination of human    Vλ and Jλ gene segments; the method comprising expressing said light    chains in the vertebrate and optionally isolating one or more of    said light chains (eg, as part of a 4-chain antibody).

In one embodiment, the method further comprises isolating from thevertebrate a lambda light chain comprising a variable region derivedfrom recombination of human Vλ and Jλ gene segments. In an example, themethod comprises immunising the mouse with an antigen (eg, a humanantigen) prior to isolating the lambda light chain. In an example, thelight chain is part of an antibody, eg, an antibody that specificallybinds the antigen.

In one embodiment, the use further comprises isolating splenic tissue(eg, the spleen) from the mouse; optionally followed by isolating atleast one antigen-specific B-cell from the tissue, wherein the B-cell(s)expresses said lambda light chain. For example, said lambda light chainis provided by an antibody that specifically binds a predeterminedantigen (eg, a human antigen). In one example, the use comprisesimmunising the mouse with the antigen (eg, a human antigen) prior toisolating the splenic tissue or lambda light chain. In an example, theuse comprises isolating the lambda light chain produced by the B-cell(or by a hybridoma produced by fusion of the B-cell with a myelomacell). In an example, the use comprises making a hybridoma from a B-cellisolated from the splenic tissue, wherein the hybridoma expresses saidlambda light chain or a derivative thereof. Optionally, the usecomprises making a derivative of the isolated antibody or lambda lightchain. Examples of derivative antibodies (according to any aspectherein) are antibodies that have one or more mutations compared to theisolated antibody (eg, to improve antigen-binding affinity and/or toenhance or inactivate Fc function) Such mutants specifically bind theantigen. Mutation or adaptation to produce a derivative includes, eg,mutation to produce Fc enhancement or inactivation. A derivative can bean antibody following conjugation to a toxic payload or reporter orlabel or other active moiety. In another example, a chimaeric antibodychain or antibody isolated from a cell of vertebrate of the invention ismodified by replacing one or all human constant regions thereof by acorresponding human constant region. For example, all constant regionsof an antibody isolated from such a cell or vertebrate are replaced withhuman constant regions to produce a fully human antibody (ie, comprisinghuman variable and constant regions). Such an antibody is useful foradministration to human patients to reduce anti-antibody reaction by thepatient.

-   61. A method of expressing immunoglobulin light chains in a    non-human vertebrate (eg, a mouse or rat), wherein at least 60% (for    example, at least 65, 70, 80, 84, 85, 90, 95, 96, 97, 98 or 99%) of    the light chains expressed by the vertebrate are provided by human    lambda light chains, the method comprising providing in the genome    of the vertebrate an Ig gene segment repertoire produced by targeted    insertion of human Ig gene segments into one or more endogenous Ig    loci, the genome comprising (i) human Vλ and Jλ gene segments    upstream of a constant region, wherein the human Vλ and Jλ gene    segments are provided by inserting at least the functional human Vλ    and Jλ (optionally also human Cλ) gene segments (and optionally    inter-gene segment sequences) comprised by a human lambda chain Ig    locus from Vλ2-18 to Cλ7 into an endogenous light chain locus of the    vertebrate and (ii) kappa V gene segments upstream of a constant    region, wherein the vertebrate expresses immunoglobulin light chains    comprising human lambda variable regions (human lambda light chains)    and at least 60% (for example, greater than 65, 70, 80, 84, 85, 90,    95, 96, 97, 98 or 99%) of the light chains expressed by the    vertebrate are provided by said human lambda light chains; the    method comprising expressing said light chains in the vertebrate and    optionally isolating one or more of said light chains (eg, as part    of a 4-chain antibody).

In one embodiment, the method further comprises isolating from thevertebrate a lambda light chain comprising a variable region derivedfrom recombination of human Vλ and Jλ gene segments. In an example, themethod comprises immunising the mouse with an antigen (eg, a humanantigen) prior to isolating the lambda light chain. In an example, thelight chain is part of an antibody, eg, an antibody that specificallybinds the antigen.

In one embodiment, the use further comprises isolating splenic tissue(eg, the spleen) from the mouse; optionally followed by isolating atleast one antigen-specific B-cell from the tissue, wherein the B-cell(s)expresses said lambda light chain. For example, said lambda light chainis provided by an antibody that specifically binds a predeterminedantigen (eg, a human antigen). In one example, the use comprisesimmunising the mouse with the antigen (eg, a human antigen) prior toisolating the splenic tissue or lambda light chain. In an example, theuse comprises isolating the lambda light chain produced by the B-cell(or by a hybridoma produced by fusion of the B-cell with a myelomacell). In an example, the use comprises making a hybridoma from a B-cellisolated from the splenic tissue, wherein the hybridoma expresses saidlambda light chain or a derivative thereof. Optionally, the usecomprises making a derivative of the isolated antibody or lambda lightchain. Examples of derivative antibodies (according to any aspectherein) are antibodies that have one or more mutations compared to theisolated antibody (eg, to improve antigen-binding affinity and/or toenhance or inactivate Fc function) Such mutants specifically bind theantigen.

-   62. A method of expressing human immunoglobulin VJC light chains in    a non-human vertebrate (eg, a mouse or rat), the method comprising    providing in the genome of the vertebrate an Ig gene segment    repertoire produced by targeted insertion of human Ig gene segments    into one or more endogenous Ig loci, wherein the method comprises    inserting at least the functional human Vλ, Jλ and Cλ gene segments    (and optionally inter-gene segment sequences) comprised by a human    lambda chain Ig locus from Vλ3-1 to Cλ7 (eg, comprised by a human    lambda chain Ig locus from 2-18 to Cλ7) into an endogenous non-human    vertebrate kappa light chain locus upstream of an endogenous    non-human vertebrate kappa constant region for expression of a human    VJC light chain; the method comprising expressing said light chains    in the vertebrate and optionally isolating one or more of said light    chains (eg, as part of a 4-chain antibody).

In one embodiment, the method further comprises isolating from thevertebrate a lambda light chain comprising a variable region derivedfrom recombination of human Vλ and Jλ gene segments. In an example, themethod comprises immunising the mouse with an antigen (eg, a humanantigen) prior to isolating the lambda light chain. In an example, thelight chain is part of an antibody, eg, an antibody that specificallybinds the antigen.

In one embodiment, the use further comprises isolating splenic tissue(eg, the spleen) from the mouse; optionally followed by isolating atleast one antigen-specific B-cell from the tissue, wherein the B-cell(s)expresses said lambda light chain. For example, said lambda light chainis provided by an antibody that specifically binds a predeterminedantigen (eg, a human antigen). In one example, the use comprisesimmunising the mouse with the antigen (eg, a human antigen) prior toisolating the splenic tissue or lambda light chain. In an example, theuse comprises isolating the lambda light chain produced by the B-cell(or by a hybridoma produced by fusion of the B-cell with a myelomacell). In an example, the use comprises making a hybridoma from a B-cellisolated from the splenic tissue, wherein the hybridoma expresses saidlambda light chain or a derivative thereof. Optionally, the usecomprises making a derivative of the isolated antibody or lambda lightchain. Examples of derivative antibodies (according to any aspectherein) are antibodies that have one or more mutations compared to theisolated antibody (eg, to improve antigen-binding affinity and/or toenhance or inactivate Fc function) Such mutants specifically bind theantigen.

-   63. The method of any one of aspects 38 to 40, optionally wherein    the vertebrate is according to any one of the other aspects.-   64. An antibody light chain isolated according to the method of any    one of aspects 58 to 63 or a derivative thereof, or an antibody    comprising such a light chain or derivative; optionally for use in    medicine.-   65. Use of an antibody light chain isolated according to the method    of any one of aspects 58 to 63 or a derivative thereof (or an    antibody comprising such a light chain or derivative) in medicine.-   66. A non-human vertebrate (eg, a mouse or rat) according to any one    of aspects 1 to 53 for expressing light chains comprising lambda    variable regions (lambda light chains), wherein at least 70% (for    example, at least 70, 75, 80, 84, 85, 90, 95, 96, 97, 98 or 99% or    100%) of the variable regions of the lambda light chains expressed    by the vertebrate are derived from recombination of human Vλ and Jλ    gene segments.

A non-human vertebrate (eg, a mouse or rat) according to any one ofaspects 1 to 53 expressing light chains comprising lambda variableregions (lambda light chains), wherein at least 70% (for example, atleast 70, 75, 80, 84, 85, 90, 95, 96, 97, 98 or 99% or 100%) of thevariable regions of the lambda light chains expressed by the vertebrateare derived from recombination of human Vλ and Jλ gene segments.

-   67. A non-human vertebrate (eg, a mouse or rat) according to any one    of aspects 1 to 53 for expressing light chains, wherein at least 60%    (for example, greater than 65, 70, 80, 84, 85, 90, 95, 96, 97, 98 or    99% or 100%) of the light chains expressed by the vertebrate are    provided by human lambda light chains.

A non-human vertebrate (eg, a mouse or rat) according to any one ofaspects 1 to 53 expressing light chains, wherein at least 60% (forexample, greater than 65, 70, 80, 84, 85, 90, 95, 96, 97, 98 or 99% or100%) of the light chains expressed by the vertebrate are provided byhuman lambda light chains.

-   68. A non-human vertebrate (eg, a mouse or rat) according to aspect    7 for expressing light chains comprising lambda variable regions    (lambda light chains), wherein expression of lambda light chains    comprising human lambda variable regions dominates over expression    of lambda light chains comprising endogenous non-human vertebrate    lambda variable regions: and optionally for inactivating expression    of endogenous non-human vertebrate lambda variable regions from the    endogenous light chain locus.

A non-human vertebrate (eg, a mouse or rat) according to aspect 7expressing light chains comprising lambda variable regions (lambda lightchains), wherein expression of lambda light chains comprising humanlambda variable regions dominates over expression of lambda light chainscomprising endogenous non-human vertebrate lambda variable regions: andoptionally for inactivating expression of endogenous non-humanvertebrate lambda variable regions from the endogenous light chainlocus.

-   69. A non-human vertebrate (eg, a mouse or rat) according to aspect    7, 8, 9 or 10 for inactivating expression of endogenous non-human    vertebrate lambda variable regions from the endogenous light chain    locus.

The percentage expression or level of expression of antibody chains canbe determined at the level of light chain mRNA transcripts in B-cells(eg, peripheral blood lymphocytes). Alternatively or additionally, thepercentage expression is determined at the level of antibody lightchains in serum or blood of the vertebrates. Additionally oralternatively, the expression can be determined by FACS (fluorescenceactivated cell sorting) analysis of B cells. For example, by assessingmouse C kappa or human C lambda expression on cell surface when thehuman lambda variable regions are expressed with mouse C kappa or humanC lambda regions respectively.

The term a “lambda light chain” in these aspects refers to a light chaincomprising a variable region sequence (at RNA or amino acid level)derived from the recombination of Vλ and Jλ gene segments. Thus a “humanlambda variable region”, for example, is a variable region derived fromthe recombination of human Vλ and Jλ gene segments. The constant regioncan be a kappa or lambda constant region, eg, a human or mouse constantregion.

The vertebrate in these aspects is, for example naïve (ie, not immunisedwith a predetermined antigen, as the term is understood in the art; forexample, such a vertebrate that has been kept in a relatively sterileenvironment as provided by an animal house used for R&D). In anotherexample, the vertebrate has been immunised with a predetermined antigen,eg, an antigen bearing a human epitope.

Reference to “functional” human gene segments acknowledges that in ahuman Ig lambda locus some V gene segments are non-functionalpseudogenes (eg, Vλ3-17, Vλ3-15, Vλ3-13, Vλ3-7, Vλ3-6, Vλ2-5, Vλ3-4,Vλ3-2; see the IMGT database: at World Wide Web (www)imgt.org/IMGTrepertoire/index.php?section=LocusGenes&repertoire=locus&species=human&group=IGL. Also, Jλ4-Cλ4 and Jλ5-Cλ5 are not functional in humans. Theterm “functional” when referring to gene segments excludes pseudogenes.An example of functional human Vλ gene segments is the group Vλ2-18,Vλ3-16, V2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3 and Vλ3-1. Anexample of functional human Jλ gene segments is the group Jλ1, Jλ2 andJλ3; or Jλ1, Jλ2 and Jλ7; or Jλ2, Jλ3 and Jλ7; or Jλ1, Jλ2, Jλ3 and Jλ7.An example of functional human Cλ gene segments is the group Cλ1, Cλ2and Cλ3; or Cλ1, Cλ2 and Cλ7; or Cλ2, Cλ3 and Cλ7; or Cλ1, Cλ2, Cλ3 andCλ7.

In one embodiment, the lambda light chains, together with heavy chainsexpressed in the cells or vertebrates of the invention, form antibodies.The heavy chains can be expressed from a transgenic heavy chain locus asherein described. For example the genome of the cell or vertebratecomprises a heavy chain locus in which is a chimaeric immunoglobulinheavy chain locus comprising one or more human V gene segments, one ormore human D gene segments and one or more human J gene segmentsupstream of a mu constant region of said non-human species; endogenousheavy chain expression has been substantially inactivated; and the heavychain locus comprises an Eμ a enhancer of said non-human vertebratespecies.

In one embodiment of the vertebrate or cell, all endogenous enhancersare deleted from the endogenous locus in which the human gene segmentsare inserted. Thus, when a human enhancer (eg, Eλ) is inserted, thiscontrols the transgenic locus in the absence of the effect of other,endogenous, enhancers (for example, kappa enhancers if the locus is anendogenous kappa enhancer). This may be useful to avoid non-humanvertebrate-like kappa:lambda expression ratios (eg, to steer expressionto a higher ratio of lambda:kappa in mice).

When endogenous light chain (eg, kappa or lambda) expression issubstantially inactive or inactivated as described herein, less than 10,5, 4, 3, 2, 1 or 0.5% of such endogenous light chains are expressed orexpressible. In one example, there is complete inactivation so no suchlight chains are expressed or expressible.

Optionally the vertebrate of the invention is naïve. Thus, thevertebrate has not been immunised with a predetermined antigen.

Where, for example, a cell of the invention is an ES cell or other IPSstem cell or other pluripotent stem cell, the cell can develop into avertebrate of the invention. For example, the cell can be implanted intoa blastocyst from a foster mother and developed into an embryo andanimal according to standard techniques.

In one embodiment, where human kappa gene segments are inserted, eachinsertion comprises human kappa gene segments

(i) Vκ1-5, Vκ1-6, Vκ1-8 and Vκ1-9 (and optionally Vκ5-2 and Vκ4-1); or

(ii) Vκ1-5, Vκ1-6, Vκ1-8, Vκ1-9, Vκ3-11, Vκ1-12, Vκ3-15, Vκ1-16, Vκ1-17,Vκ3-20 (and optionally Vκ 2-24 and/or Vκ1-13); or

(iii) Vκ1-5, Vκ1-6, Vκ1-8, Vκ1-9, Vκ3-11, Vκ1-12, Vκ3-15, Vκ1-16,Vκ1-17, Vκ3-20, Vκ 2-24, Vκ1-27, Vκ2-28, Vκ2-30 and Vκ1-33 (andoptionally Vκ 2-29 and/or Vκ2-40 and/or Vκ1-39);

and optionally

(iv) Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5.

In one embodiment, the human kappa insertion also comprises a human iEκand/or human 3′Eκ downstream of the human J gene segments in the locus.

Transgenic Mice of the Invention Expressing Essentially ExclusivelyHuman Heavy Chain Variable Regions Develop Normal Splenic and BMCompartments & Normal Ig Expression In Which the Ig Comprise Human HeavyChain Variable Regions

The present inventors surprisingly observed normal Ig subtype expression& B-cell development in transgenic mice of the invention expressingantibodies with human heavy chain variable regions substantially in theabsence of endogenous heavy and kappa chain expression. See Example 16below.

The inventors observed that surprisingly the inactivation of endogenousheavy chain variable region expression in the presence of human variableregion expression does not change the ratio of B-cells in the spleniccompartment (FIG. 66) or bone marrow B progenitor compartment (FIG. 67)and the immunoglobulin levels in serum are normal and the correct Igsubtypes are expressed (FIG. 68). These data demonstrate that insertedhuman heavy chain gene segments according to the invention (eg, aninsertion of at least human V_(H) gene segments V_(H)2-5, 7-4-1, 4-4,1-3, 1-2, 6-1, and all the human D and J_(H) gene segments D1-1, 2-2,3-3, 4-4, 5-5, 6-6, 1-7, 2-8, 3-9, 5-12, 6-13, 2-15, 3-16, 4-17, 6-19,1-20, 2-21, 3-22, 6-25, 1-26 and 7-27; and J1, J2, J3, J4, J5 and J6)are fully functional for VDJ gene segment rearrangement from thetransgenic heavy chain locus, B-cell receptor (BCR) signalling andproper B-cell maturation

The invention therefore provides the following aspects (numberingstarting at aspect 70):—

-   70. A mouse that expresses or for expressing immunoglobulin heavy    chains comprising human variable regions, wherein the heavy chains    expressed by the mouse are essentially exclusively said heavy chains    comprising human variable regions; and said heavy chains comprising    human variable regions are expressed as part of serum IgG1, IgG2b    and IgM (and optionally IgG2a) antibodies in the mouse;

the mouse comprising an immunoglobulin heavy chain locus comprisinghuman VH, DH and JH gene segments upstream of a mouse constant region(eg, C-mu and/or C-delta and/or C-gamma; such as (in a 5′ to 3′orientation) mouse C-mu and mouse C-delta and mouse C-gamma), wherein

(a) the mouse is capable of expressing immunoglobulin heavy chainscomprising human variable regions and the heavy chains expressed by themouse are essentially exclusively said heavy chains comprising humanvariable regions; and

(b) the mouse expresses serum IgG1, IgG2b and IgM (and optionally IgG2a)antibodies comprising said heavy chains.

Ig isotypes can be determined, for example, using isotype-matched toolantibodies as will be readily familiar to the skilled person (and asillustrated in Example 16).

In an embodiment, the mouse is naïve.

-   71. The mouse of aspect 70 for expressing a normal relative    proportion of serum IgG1, IgG2a, IgG2b and IgM antibodies.

By “normal” is meant comparable to expression in a mouse (eg, a naïvemouse) expressing only mouse antibody chains, eg, a mouse whose genomecomprises only wild-type functional Ig heavy and light chain loci, eg, awild-type mouse.

-   72. The mouse of aspect 70 or 71, wherein the mouse expresses a    normal relative proportion of serum IgG1, IgG2a, IgG2b and IgM    antibodies.

By “normal” is meant comparable to expression in a mouse (eg, a naïvemouse) expressing only mouse antibody chains, eg, a mouse whose genomecomprises only wild-type functional Ig heavy and light chain loci, eg, awild-type mouse.

-   73. The mouse of any one of aspects 70 to 72, for expressing in the    mouse

(i) serum IgG1 at a concentration of about 25-350 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-800 μg/ml; and

(iv) serum IgM at a concentration of about 50-300 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-600 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-700 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

For example, the mouse of any one of aspects 70 to 72, for expressing inthe mouse

(i) serum IgG1 at a concentration of about 25-150 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-300 μg/ml; and

(iv) serum IgM at a concentration of about 50-200 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-200 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-400 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

The mouse of any one of aspects 70 to 72, for expressing in the mouse Igin the relative proportions of

(i) serum IgG1 at a concentration of about 25-350 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-800 μg/ml; and

(iv) serum IgM at a concentration of about 50-300 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-600 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-700 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

For example, the mouse of any one of aspects 70 to 72, for expressing inthe mouse Ig in the relative proportions of

(i) serum IgG1 at a concentration of about 25-150 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-300 μg/ml; and

(iv) serum IgM at a concentration of about 50-200 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-200 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-400 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

-   74. The mouse of any one of aspects 70 to 73, wherein the mouse    expresses

(i) serum IgG1 at a concentration of about 25-350 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-800 μg/ml; and

(iv) serum IgM at a concentration of about 50-300 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-600 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-700 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

For example, the mouse of any one of aspects 70 to 72, the mouseexpresses

(i) serum IgG1 at a concentration of about 25-150 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-300 μg/ml; and

(iv) serum IgM at a concentration of about 50-200 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-200 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-400 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

The mouse of any one of aspects 70 to 73, wherein the mouse expresses Igin the relative proportions of

(i) serum IgG1 at a concentration of about 25-350 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-800 μg/ml; and

(iv) serum IgM at a concentration of about 50-300 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-600 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-700 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

For example, the mouse of any one of aspects 70 to 72, the mouseexpresses Ig in the relative proportions of

(i) serum IgG1 at a concentration of about 25-150 μg/ml;

(ii) serum IgG2a at a concentration of about 0-200 μg/ml;

(iii) serum IgG2b at a concentration of about 30-300 μg/ml; and

(iv) serum IgM at a concentration of about 50-200 μg/ml;

or

(i) serum IgG1 at a concentration of about 10-200 μg/ml;

(ii) serum IgG2a at a concentration of about 0-500 μg/ml;

(iii) serum IgG2b at a concentration of about 20-400 μg/ml; and

(iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by Ig capture on a plate followed by incubation (eg, forone hour at RT, eg, for one hour at 20° C.) with anti-mouseisotype-specific labelled antibodies and quantification of Ig using thelabel (eg, using anti-mouse Ig isotype specific antibodies eachconjugated to horseradish peroxidase conjugated at a ratio of 1/10000 inPBS with 0.1% Tween™, followed by development of the label withtetramethylbenzidine substrate (TMB) for 4-5 minutes in the dark at roomtemperature (eg, 20° C.), adding sulfuric acid to stop development ofthe label and reading of the label at 450 nm).

-   75. The mouse of any one of aspects 70 to 74 for expressing said    heavy chains from splenic B-cells in a mouse that produces a normal    proportion or percentage of mature splenic B-cells, eg as determined    by FACS.

By “normal” is meant comparable to mature splenic B-cell production in amouse (eg, a naïve mouse) expressing only mouse antibody chains, eg, amouse whose genome comprises only wild-type functional Ig heavy andlight chain loci, eg, a wild-type mouse.

For example, at least 40, 50, 60 or 70% of total splenic B-cellsproduced by the mouse of the invention are mature B-cells. SplenicB-cells are B220⁺ and express B220 at relatively high levels as theskilled person will know. Mature splenic B-cells express B220 and IgD,both at relatively high levels as will be known by the skilled person.IgM expression is relatively low in mature splenic B-cells, again as isknown in the art. For example, see J Exp Med. 1999 Jul. 5; 190(1):75-89;“B cell development in the spleen takes place in discrete steps and isdetermined by the quality of B cell receptor-derived signals”; Loder Fet al.

Optionally the mouse produces a normal ratio of T1, T2 and maturesplenic B-cells, eg, as determined by FACS. For example, the mouse ofthe invention produces about 40-70% mature splenic B-cells, 15-35%splenic T1 cells; and 5-10% splenic T2 cells (percentage with referenceto the total splenic B220-positive (high) population). For example,about 40-60% mature splenic B-cells, 15-30% splenic T1 cells; and 5-10%splenic T2 cells. By “normal” is meant comparable to a T1/T2/maturesplenic B-cell proportion in a mouse (eg, a naïve mouse) expressing onlymouse antibody chains, eg, a mouse whose genome comprises only wild-typefunctional Ig heavy and light chain loci, eg, a wild-type mouse.

-   76. The mouse of any one of aspects 70 to 75, wherein the mouse    produces a normal proportion or percentage of mature splenic    B-cells, eg as determined by FACS.-   77. A mouse that expresses or for expressing immunoglobulin heavy    chains comprising human variable regions, wherein the heavy chains    expressed by the mouse are essentially exclusively said heavy chains    comprising human variable regions and are expressed in a mouse that    produces a normal proportion or percentage of mature splenic B-cells    (eg, as determined by FACS); the mouse comprising an immunoglobulin    heavy chain locus comprising human VH, DH and JH gene segments    upstream of a mouse constant region (eg, C-mu and/or C-delta and/or    C-gamma; such as (in a 5′ to 3′ orientation) and wherein the mouse    produces a normal proportion or percentage of mature splenic    B-cells. By “normal” is meant comparable to mature splenic B-cell    production in a mouse (eg, a naïve mouse) expressing only mouse    antibody chains, eg, a mouse whose genome comprises only wild-type    functional Ig heavy and light chain loci, eg, a wild-type mouse.

For example, at least 40, 50, 60 or 70% of total splenic B-cellsproduced by the mouse of the invention are mature B-cells. SplenicB-cells are B220⁺ and express B220 at relatively high levels as theskilled person will know. Mature splenic B-cells express B220 and IgD,both at relatively high levels as will be known by the skilled person.IgM expression is relatively low in mature splenic B-cells, again as isknown in the art. For example, see J Exp Med. 1999 Jul. 5; 190(1):75-89;“B cell development in the spleen takes place in discrete steps and isdetermined by the quality of B cell receptor-derived signals”; Loder Fet al.

Optionally the mouse produces a normal ratio of T1, T2 and maturesplenic B-cells, eg, as determined by FACS. For example, the mouse ofthe invention produces about 40-70% mature splenic B-cells, 15-35%splenic T1 cells; and 5-10% splenic T2 cells (percentage with referenceto the total splenic B220-positive (high) population). For example,about 40-60% mature splenic B-cells, 15-30% splenic T1 cells; and 5-10%splenic T2 cells. By “normal” is meant comparable to a T1/T2/maturesplenic B-cell proportion in a mouse (eg, a naïve mouse) expressing onlymouse antibody chains, eg, a mouse whose genome comprises only wild-typefunctional Ig heavy and light chain loci, eg, a wild-type mouse.

-   78. The mouse of any one of aspects 70 to 77 for expressing said    heavy chains in a mouse that produces a normal proportion or    percentage of bone marrow B-cell progenitor cells (eg as determined    by FACS).

In one embodiment, the mouse is for expressing said heavy chains in amouse that produces a normal proportion or percentage of bone marrowpre-, pro and prepro-B-cells (eg as determined by FACS). See J Exp Med.1991 May 1; 173(5):1213-25; “Resolution and characterization of pro-Band pre-pro-B cell stages in normal mouse bone marrow”; Hardy R R et alfor more discussion on progenitor cells.

By “normal” is meant comparable to bone marrow B-cell production in amouse (eg, a naïve mouse) expressing only mouse antibody chains, eg, amouse whose genome comprises only wild-type functional Ig heavy andlight chain loci, eg, a wild-type mouse.

-   79. The mouse of any one of aspects 70 to 78, wherein the mouse    produces a normal proportion or percentage of bone marrow B-cell    progenitor cells (eg, as determined by FACS).

In one embodiment, the mouse produces a normal proportion or percentageof bone marrow pre-, pro and prepro-B-cells (eg as determined by FACS).

By “normal” is meant comparable to bone marrow B-cell production in amouse (eg, a naïve mouse) expressing only mouse antibody chains, eg, amouse whose genome comprises only wild-type functional Ig heavy andlight chain loci, eg, a wild-type mouse.

-   80. A mouse that expresses or for expressing immunoglobulin heavy    chains comprising human variable regions, wherein the heavy chains    expressed by the mouse are essentially exclusively said heavy chains    comprising human variable regions and are expressed in a mouse that    produces a normal proportion or percentage of bone marrow B-cell    progenitor cells (eg, as determined by FACS), the mouse comprising    an immunoglobulin heavy chain locus comprising human VH, DH and JH    gene segments upstream of a mouse constant region (eg, C-mu and/or    C-delta and/or C-gamma; such as (in a 5′ to 3′ orientation) and    wherein the mouse produces a normal proportion or percentage of bone    marrow B-cell progenitor cells.

In one embodiment, the mouse is for expressing said heavy chains in amouse that produces a normal proportion or percentage of bone marrowpre-, pro and prepro-B-cells (eg as determined by FACS).

By “normal” is meant comparable to bone marrow B-cell production in amouse (eg, a naïve mouse) expressing only mouse antibody chains, eg, amouse whose genome comprises only wild-type functional Ig heavy andlight chain loci, eg, a wild-type mouse.

-   81. The mouse of any one of aspects 70 to 80, wherein at least 90%    of the heavy chains are heavy chains comprising human variable    regions.

For example, at least 90, 95, 96, 97, 98, 99 or 99.5% or 100% of theheavy chains comprise human variable regions, ie, variable regionsderived from the recombination of human VH with human D and JH genesegments.

-   82. The mouse of any one of aspects 70 to 81, wherein the mouse    constant region comprises a mouse C-mu region, a C-delta region and    a C-gamma region.

In one embodiment, each of the C regions is an endogenous, mouseC-region. In one embodiment at least the C-mu and the C-delta regionsare mouse C regions. This is useful for harnessing the endogenouscontrol mechanisms involved in the development of the various B-celltypes and progenitors in the spleen and bone marrow.

In one embodiment, the C-gamma region is a human C-gamma region. This isbeneficial for producing class-switched gamma-type heavy chains in themouse in which essentially all of the expressed heavy chains have humanvariable regions and human constant regions.

-   83. The mouse of any one of aspects 70 to 82, wherein there is a    mouse heavy chain enhancer between the human gene segments and the    mouse constant region. This is useful for harnessing the endogenous    mouse antibody- and B-cell development control mechanisms.-   84. The mouse of any one of aspects 70 to 83, wherein there is a    mouse S-mu switch between the human gene segments and the mouse    constant region.-   85. The mouse of any one of aspects 70 to 84, wherein the genome of    the mouse comprises endogenous mouse heavy chain locus V, D and J    gene segments upstream of the human gene segments.-   86. The mouse of aspect 85, wherein the mouse V, D and J gene    segments are present together with the endogenous inter-gene segment    sequences.-   87. The mouse of aspect 85 or 86, wherein the mouse gene segments    are in inverted orientation. Thus, they are inverted with respect to    the wild-type orientation in a mouse genome. They are thus inverted    relative to the orientation of the mouse constant region.-   88. The mouse of any one of aspects 70 to 87, wherein the mouse    expresses light chains comprising human variable regions (eg, kappa    light chains comprising human kappa variable regions). Thus, the    human variable regions are derived from the recombination of human    VL and JL gene segments, eg, human Vκ and human Jκ.-   89. The mouse of aspect 88, comprising human Vκ and Jκ gene segments    upstream of a mouse CL (eg, endogenous Cκ); optionally wherein the    human Vκ and Jκ gene segments comprise Vκ2-24, Vκ3-20, Vκ1-17,    Vκ1-16, Vκ3-15, Vκ1-13, Vκ1-12, Vκ3-11, Vκ1-9, Vκ1- 8, Vκ1-6, Vκ1-5,    Vκ5-2, Vκ4-1, Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5.-   90. The mouse of any one of aspects 70 to 89, wherein the human VH,    DH and JH gene segments comprise human V_(H) gene segments V_(H)2-5,    7-4-1, 4-4, 1-3, 1-2, 6-1, and all the human D and J_(H) gene    segments D1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 1-7, 2-8, 3-9, 5-12, 6-13,    2-15, 3-16, 4-17, 6-19, 1-20, 2-21, 3-22, 6-25, 1-26 and 7-27; and    J1, J2, J3, J4, J5 and J6. For example, the human VH, DH and JH gene    segments comprise human V_(H) gene segments V_(H)2-5, 7-4-1, 4-4,    1-3, 1-2, 6-1, and all the human D and JH gene segments D1-1, 2-2,    3-3, 4-4, 5-5, 6-6, 1-7, 2-8, 3-9, 3-10, 4-11, 5-12, 6-13, 1-14,    2-15, 3-16, 4-17, 5-18, 6-19, 1-20, 2-21, 3-22, 4-23, 5-24, 6-25,    1-26 and 7-27; and J1, J2, J3, J4, J5 and J6.-   91. Use of the mouse of any one of aspects 70 to 90 for expressing    immunoglobulin heavy chains comprising human variable regions,    wherein the heavy chains expressed by the mouse are essentially    exclusively said heavy chains comprising human variable regions; and    said heavy chains comprising human variable regions are expressed as    part of serum IgG1, IgG2b and IgM (and optionally IgG2a) antibodies    in the mouse. The use is non-therapeutic, non-diagnostic and    non-surgical use.

In one embodiment, the use comprises immunising the mouse with anantigen (eg, a human antigen) and isolating an IgG1 antibody thatspecifically binds the antigen.

In one embodiment, the use comprises immunising the mouse with anantigen (eg, a human antigen) and isolating an IgG2a antibody thatspecifically binds the antigen.

In one embodiment, the use comprises immunising the mouse with anantigen (eg, a human antigen) and isolating an IgG2b antibody thatspecifically binds the antigen.

Optionally, the use comprises making a derivative of the isolatedantibody. Examples of derivative antibodies (according to any aspectherein) are antibodies that have one or more mutations compared to theisolated antibody (eg, to improve antigen-binding affinity and/or toenhance or inactivate Fc function) Such mutants specifically bind theantigen.

-   92. Use of the mouse of any one of aspects 70 to 90 for expressing    immunoglobulin heavy chains comprising human variable regions,    wherein the heavy chains expressed by the mouse are essentially    exclusively said heavy chains comprising human variable regions and    are expressed in a mouse that produces a normal proportion or    percentage of mature splenic B-cells. The use is non-therapeutic,    non-diagnostic and non-surgical use.

In one embodiment, the use further comprises isolating splenic tissue(eg, the spleen) from the mouse; optionally followed by isolating atleast one antigen-specific B-cell from the tissue, wherein the B-cell(s)expresses an antibody that specifically binds a predetermined antigen.In one example, the use comprises immunising the mouse with the antigenprior to isolating the splenic tissue. In an example, the use comprisesisolating an antibody produced by the B-cell (or by a hybridoma producedby fusion of the B-cell with a myeloma cell). Optionally, the usecomprises making a derivative of the isolated antibody. Examples ofderivative antibodies (according to any aspect herein) are antibodiesthat have one or more mutations compared to the isolated antibody (eg,to improve antigen-binding affinity and/or to enhance or inactivate Fcfunction) Such mutants specifically bind the antigen.

-   93. Use of the mouse of any one of aspects 70 to 90 for expressing    immunoglobulin heavy chains comprising human variable regions,    wherein the heavy chains expressed by the mouse are essentially    exclusively said heavy chains comprising human variable regions and    are expressed in a mouse that produces a normal proportion or    percentage of bone marrow B-cell progenitor cells. The use is    non-therapeutic, non-diagnostic and non-surgical use.-   94. Use of the mouse of any one of aspects 70 to 90 for the purpose    stated in one or more of aspects 70, 71, 73, 75 and 78.

The expression (eg, percentage expression or expression proportion orlevel) of Ig can be determined at the level of antibody chain mRNAtranscripts in B-cells (eg, peripheral blood lymphocytes). Alternativelyor additionally, the percentage expression is determined at the level ofantibody in serum or blood of the vertebrates. Additionally oralternatively, the expression can be determined by FACS analysis of Bcells.

In these aspects, “heavy chains comprising human variable regions” meansvariable regions derived from the recombination of human VH, D and JHgene segments.

“Essentially exclusively” the expressed heavy chains comprise humanvariable regions, ie, there is only a relatively very low or even noendogenous mouse heavy chain variable region expression. For example, atleast 90, 95, 96, 97, 98, 99 or 99.5% or 100% of the heavy chains areheavy chains comprising human variable regions. In one embodiment, atleast 90% of the heavy chains are heavy chains comprising human variableregions. The percentage expression can be determined at the level ofheavy chain mRNA transcripts in B-cells (eg, peripheral bloodlymphocytes). Alternatively or additionally, the percentage expressionis determined at the level of heavy chains or antibodies in serum orblood of the mice. Additionally or alternatively, the expression can bedetermined by FACS analysis of B-cells.

The mouse can comprise any endogenous heavy chain locus in which humanV, D and J gene segments are present, as described herein. In oneexample, the mouse genome comprises a mouse heavy chain locus in whichat least human V_(H) gene segments V_(H)2-5, 7-4-1, 4-4, 1-3, 1-2, 6-1,and all the human D and J_(H) gene segments D1-1, 2-2, 3-3, 4-4, 5-5,6-6, 1-7, 2-8, 3-9, 5-12, 6-13, 2-15, 3-16, 4-17, 6-19, 1-20, 2-21,3-22, 6-25, 1-26 and 7-27; and J1, J2, J3, J4, J5 and J6 are upstream ofthe mouse constant region.

The vertebrate in these aspects is, for example naïve (ie, not immunisedwith a predetermined antigen, as the term is understood in the art; forexample, such a vertebrate that has been kept in a relatively sterileenvironment as provided by an animal house used for R&D). In anotherexample, the vertebrate has been immunised with a predetermined antigen,eg, an antigen bearing a human epitope.

In one embodiment, the heavy chains, together with light chainsexpressed in the mice of the invention, form antibodies (Ig). The lightchains can be expressed from any transgenic light chain locus as hereindescribed. For example the genome of the mouse comprises a heavy chainlocus in which is a chimaeric immunoglobulin heavy chain locuscomprising one or more human V gene segments, one or more human D genesegments and one or more human J gene segments upstream of a mu constantregion of said non-human species; endogenous heavy chain expression hasbeen substantially inactivated; and the heavy chain locus comprises anEta enhancer of said non-human vertebrate species.

In one embodiment of any aspect, endogenous light chain (eg, kappaand/or lambda) expression is substantially inactive or inactivated, forexample using method as described herein. In this case, less than 10, 5,4, 3, 2, 1 or 0.5% of such endogenous lambda light chains are expressedor expressible. Additionally or alternatively, less than 10, 5, 4, 3, 2,1 or 0.5% of such endogenous kappa light chains are expressed orexpressible. In one example, there is complete inactivation ofendogenous kappa and/or lambda expression so no such light chains areexpressed or expressible.

In one embodiment, the genome of the mouse comprises human kappa genesegments

(i) Vκ1-5, Vκ1-6, Vκ1-8 and Vκ1-9 (and optionally Vκ5-2 and Vκ4-1); or

(ii) Vκ1-5, Vκ1-6, Vκ1-8, Vκ1-9, Vκ3-11, Vκ1-12, Vκ3-15, Vκ1-16, Vκ1-17,Vκ3-20 (and optionally Vκ 2-24 and/or Vκ1-13); or

(iii) Vκ1-5, Vκ1-6, Vκ1-8, Vκ1-9, Vκ3-11, Vκ1-12, Vκ3-15, Vκ1-16,Vκ1-17, Vκ3-20, Vκ 2-24, Vκ1-27, Vκ2-28, Vκ2-30 and Vκ1-33 (andoptionally Vκ 2-29 and/or Vκ2-40 and/or Vκ1-39);

and optionally

(iv) Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5.

In one embodiment, the genome also comprises (i) at least human V_(H)gene segments V_(H)2-5, 7-4-1, 4-4, 1-3, 1-2, 6-1, and all the human Dand J_(H) gene segments D1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 1-7, 2-8, 3-9,5-12, 6-13, 2-15, 3-16, 4-17, 6-19, 1-20, 2-21, 3-22, 6-25, 1-26 and7-27; and J1, J2, J3, J4, J5 and J6 and (ii) at least human genesegments Vκ2-24, Vκ3-20, Vκ1-17, Vκ1-16, Vκ3-15, Vκ1-13, Vκ1-12, Vκ3-11,Vκ1-9, Vκ1-8, Vκ1-6, Vκ1-5, Vκ5-2, Vκ4-1, Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5. Asdemonstrated in Example 16, such mice are fully functional in the aspectof rearrangement, BCR signalling and B cell maturation. Greater than 90%of the antibodies expressed by the mice comprised human heavy chainvariable regions and human kappa light chain variable regions. Thesemice are, therefore, very useful for the selection of antibodies havinghuman variable regions that specifically bind human antigen followingimmunisation of the mice with such antigen. Following isolation of suchan antibody, the skilled person can replace the mouse constant regionswith human constant regions using conventional techniques to arrive attotally human antibodies which are useful as drug candidates foradministration to humans (optionally following mutation or adaptation toproduce a further derivative, eg, with Fc enhancement or inactivation orfollowing conjugation to a toxic payload or reporter or label or otheractive moiety).

In one embodiment, the genome also comprises a human iEκ and/or human3′Eκ downstream of the human J gene segments in the locus.

The invention also includes the following clauses:

Clause 1. A mouse that expresses immunoglobulin heavy chains containinghuman variable regions,

-   -   wherein the mouse comprises a genome that includes an        immunoglobulin heavy chain locus comprising human VH, DH, and JH        gene segments positioned upstream to a mouse constant region;    -   wherein the mouse expresses immunoglobulin heavy chains,        characterized in that at least 90% of the immunoglobulin heavy        chains expressed by the mouse comprise a human variable region;        and    -   wherein the mouse expresses serum IgG1, IgG2b, and IgM        antibodies comprising said heavy chains containing a human        variable region.

Clause 2. A mouse that expresses immunoglobulin heavy chains containinghuman variable regions,

-   -   wherein the mouse comprises a genome that includes an        immunoglobulin heavy chain locus comprising human VH, DH, and JH        gene segments which are positioned upstream to a mouse constant        region;    -   wherein the mouse expresses immunoglobulin heavy chains,        characterized in that at least 90% of the immunoglobulin heavy        chains expressed by the mouse comprise a human variable region;        and    -   wherein the mouse produces a normal proportion of mature splenic        B-cells;    -   wherein said normal proportion is a proportion of mature splenic        B-cells produced by a mouse that expresses immunoglobulin heavy        chains containing mouse variable regions and does not express        immunoglobulin heavy chains containing human variable regions.

Clause 3. A mouse that expresses immunoglobulin heavy chains containinghuman variable regions,

-   -   wherein the mouse comprises a genome that includes an        immunoglobulin heavy chain locus comprising human VH, DH, and JH        gene segments which are positioned upstream to a mouse constant        region;    -   wherein the mouse expresses immunoglobulin heavy chains,        characterized in that it at least 90% of the immunoglobulin        heavy chains expressed by the mouse comprise a human variable        region; and    -   wherein the mouse produces a normal proportion of bone marrow        B-cell progenitor cells;    -   wherein the normal proportion is a proportion of bone marrow        B-cell progenitor cells produced by a mouse that expresses        immunoglobulin heavy chains containing mouse variable regions        and does not expresses immunoglobulin heavy chains containing        human variable regions.

Clause 4. The mouse of any of the preceding clauses, wherein the mouseexpresses a normal proportion of IgG1, IgG2b, and IgM in a sample ofserum obtained from the mouse;

-   -   wherein the normal proportion is as produced by a mouse that        expresses immunoglobulin heavy chains containing mouse variable        regions and does not expresses immunoglobulin heavy chains        containing human variable regions.

Clause 5. The mouse of any of the preceding clauses, wherein the mouseconstant region is C-mu, C-delta, and/or C-gamma.

Clause 6. The mouse of clause 5, wherein the mouse constant region is atleast C-mu, C-delta and C-gamma.

Clause 7. The mouse of any of the preceding clauses, wherein the mouseconstant region is an endogenous mouse C-region.

Clause 8. The mouse of any of the preceding clauses, wherein the mouseexpresses a human C-gamma region.

Clause 9. The mouse of any of the preceding clauses, wherein the mouseis a naïve mouse.

Clause 10. The mouse of clause 1, wherein the mouse expresses serumIgG2a comprising said heavy chains containing a human variable region.

Clause 11. The mouse of any of the preceding clauses, wherein the mouseexpresses Ig subtypes in a relative proportion of

-   -   (i) serum IgG1 at a concentration of about 25-350 μg/ml;    -   (ii) serum IgG2a at a concentration of about 0-200 μg/ml;    -   (iii) serum IgG2b at a concentration of about 30-800 μg/ml; and    -   (iv) serum IgM at a concentration of about 50-300 μg/ml;    -   Or    -   (i) serum IgG1 at a concentration of about 10-600 μg/ml;    -   (ii) serum IgG2a at a concentration of about 0-500 μg/ml;    -   (iii) serum IgG2b at a concentration of about 20-700 μg/ml; and    -   (iv) serum IgM at a concentration of about 50-700 μg/ml;    -   as determined by immunoglobulin capture on a plate followed by        incubation with an anti-mouse isotype-specific antibodies each        comprising a label and quantification of each immunoglobulin        based on the level of each label.

Clause 12. The mouse of any of the preceding clauses, wherein the mouseexpresses Ig subtypes in a relative proportion of

-   -   (i) total serum IgG and IgM at a concentration of about 200-2500        μg/ml; and    -   (ii) serum IgM at a concentration of about 100-800 μg/ml;    -   as determined by immunoglobulin capture on a plate followed by        incubation with an anti-mouse isotype-specific antibodies each        comprising a label and quantification of each immunoglobulin        based on the level of each label.

Clause 13. The mouse of any of the preceding clauses, wherein the mouseexpresses said immunoglobulin heavy chains from splenic B-cells andwherein the mouse produces a normal proportion of mature splenic B-cellsin total spleen cells comprising mature B-cells, and splenic T1 and T2cells.

Clause 14. The mouse of any one of clauses 1-3, wherein, at least 95,96, 97, 98, 99, or 99.5% of the immunoglobulin heavy chains expressed bythe mouse are immunoglobulin heavy chains comprising human variableregions.

Clause 15. The mouse of any of the preceding clauses, wherein a mouseimmunoglobulin heavy chain enhancer is positioned in said mouse heavychain immunoglobulin locus between the human VH, DH, and JH genesegments and the mouse constant region.

Clause 16. The mouse of any of the preceding clauses, wherein a mouseS-mu switch is positioned in said mouse heavy chain immunoglobulin locusbetween the human VH, DH, and JH gene segments and the mouse constantregion.

Clause 17. The mouse of any of the preceding clauses, wherein endogenousmouse immunoglobulin heavy chain V, D and J gene segments are positionedin said mouse heavy chain immunoglobulin locus upstream to the human VH,DH, and JH gene segments.

Clause 18. The mouse of clause 17, wherein the mouse immunoglobulinheavy chain V, D and J gene segments are present in said mouse heavychain immunoglobulin locus with endogenous inter-gene segment sequences.

Clause 19. The mouse of clause 17 or 18, wherein the mouseimmunoglobulin heavy chain V, D and J gene segments are positioned insaid mouse heavy chain immunoglobulin locus in an orientation that isinverted relative to its natural endogenous orientation.

Clause 20. The mouse of any of the preceding clauses, wherein the mouseexpresses light chains containing human kappa variable regions.

Clause 21. The mouse of clause 20, wherein the mouse expressesimmunoglobulin light chains derived from recombination of Vκ with humanJκ.

Clause 22. The mouse of any of the preceding clauses, wherein the mouseexpresses light chains containing human lambda variable regions.

Clause 23. The mouse of clause 22, wherein the mouse expressesimmunoglobulin light chains derived from recombination of Vλ with humanJλ.

Clause 24. The mouse of clause 21, comprising a genome that includeshuman Vκ and Jκ gene segments positioned in said mouse heavy chainimmunoglobulin locus upstream to a mouse CL.

Clause 25. The mouse of clause 24, wherein the mouse CL is an endogenousCκ.

Clause 26. The mouse of clauses 24 or 25, wherein the human Vκ and Jκgene segments comprise Vκ2-24, Vκ3-20, Vκ1-17, Vκ1-16, Vκ3-15, Vκ1-13,Vκ1-12, Vκ3-11, Vκ1-9, Vκ1-8, Vκ1-6, Vκ1-5, Vκ5-2, Vκ4-1, Jκ1, Jκ2, Jκ3,Jκ4 and Jκ5.

Clause 27. The mouse of any the preceding clauses, wherein the human VH,DH and JH gene segments contain

-   -   human VH gene segments: VH2-5, 7-4-1, 4-4, 1-3, 1-2, 6-1;    -   human DH gene segments: D1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 1-7, 2-8,        3-9, 5-12, 6-13, 2-15, 3-16, 4-17, 6-19, 1-20, 2-21, 3-22, 6-25,        1-26 and 7-27; and    -   human JH gene segments: J1, J2, J3, J4, J5 and J6.

Clause 28. A method for obtaining one or more immunoglobulin heavychains containing human variable regions, comprising providing the mouseof any of the preceding clauses and

isolating one or more immunoglobulin heavy chains.

Clause 29. The method of clause 28, wherein each immunoglobulin heavychain is included in an antibody.

Clause 30. The method of clause 29, wherein said heavy chain and/or saidantibody containing said heavy chain is modified after said isolating.

Clause 31. The method of clause 28, wherein a step of immunizing themouse with an antigen is performed before the step of isolating theimmunoglobulin heavy chains.

Clause 31a. The method of clause 30, wherein the antigen is a humanantigen.

Clause 32. The method of clause 30, 31, or 31a, wherein theimmunoglobulin heavy chains are included in an IgG1 antibody, antibodyfragment, or antibody derivative that specifically binds the antigen.

Clause 33. The method of clause 30, 31, or 31a, wherein theimmunoglobulin heavy chains are included in an IgG2a antibody, antibodyfragment, or antibody derivative that specifically binds the antigen.

Clause 34. The method of clause 30, 31, or 31a, wherein theimmunoglobulin heavy chains are included in an IgG2b antibody, antibodyfragment, or antibody derivative that specifically binds the antigen.

Clause 35. The method of clause 30, 31, or 31a, wherein theimmunoglobulin heavy chains are included in an IgM antibody, antibodyfragment, or antibody derivative that specifically binds the antigen.

Clause 36. An antibody or immunoglobulin heavy chain isolated in themethod of any one of clauses 28 to 35, or a antigen-binding fragment orderivative of the antibody or heavy chain.

Clause 37. A pharmaceutical composition comprising the antibody,antibody fragment, or antibody derivative of clause 36 and apharmaceutically acceptable carrier, excipient, or diluent.

Clause 38. A method for isolating splenic tissue comprising providingthe mouse of 1 to 27,

-   -   collecting a spleen or portion thereof from the mouse, and    -   obtaining tissue from the spleen or portion.

Clause 39. The method of clause 38, further comprising isolating atleast one antigen-specific B-cell from the splenic tissue, wherein theB-cell expresses a heavy chain containing a human variable region.

Clause 40. The method of clause 38 or 39, wherein a step of immunizingthe mouse with an antigen is performed before the step of collecting aspleen from the mouse.

Clause 41. The method of clause 40, wherein the antigen is a humanantigen.

Clause 42. The method of clause 40 or 41 wherein the at least oneantigen-specific B-cell produces an IgG1, IgG2a, IgG2b or IgM antibodycomprising said heavy chain, wherein the antibody specifically binds theantigen.

Clause 43. The method of clauses 38 to 42, wherein the at least oneantigen-specific B-cell that produces said heavy chain is fused with animmortal myeloma cell to produce a hybridoma cell.

Clause 44. The method of clauses 38 to 43, further comprising a step ofisolating an immunoglobulin heavy chain from the B-cell or the hybridomacell.

Clause 45. An antibody or immunoglobulin heavy chain isolated in themethod of clause 44, or a antigen-binding fragment or derivative of theantibody or heavy chain.

Clause 46. A pharmaceutical composition comprising the antibody,antibody fragment, or antibody derivative of clause 45 and apharmaceutically acceptable carrier, excipient, or diluent.

Clause 47. A method for obtaining a humanised antibody, comprising

-   -   selecting a mouse that expresses immunoglobulin heavy chains        containing human variable regions,    -   wherein the mouse comprises a genome that includes an        immunoglobulin heavy chain locus comprising human VH, DH, and JH        gene segments positioned upstream to a mouse constant region,    -   wherein the mouse expresses immunoglobulin heavy chains,        characterized in that at least 90% of the immunoglobulin heavy        chains expressed by the mouse are immunoglobulin heavy chains        containing a human variable region,    -   wherein the mouse expresses serum IgG1, IgG2b, and IgM        antibodies comprising said heavy chains containing a human        variable region,    -   wherein the mouse produces a normal proportion of mature splenic        B-cells,    -   wherein the mouse produces a normal proportion of bone marrow        B-cell progenitor cells, and    -   wherein the mouse expresses a normal proportion of IgG1, IgG2a,        IgG2b, and IgM in a sample of serum obtained from the mouse, and    -   wherein each said normal proportion is a proportion produced by        a mouse that expresses immunoglobulin heavy chains containing        mouse variable regions and does not expresses immunoglobulin        heavy chains containing human variable regions;    -   collecting serum from said mouse; and    -   obtaining a pool of humanised antibodies comprising IgG1, IgG2b,        and IgM antibodies from the serum.

Clause 48. The method of clause 47, comprising a step of immunizing themouse with an antigen before the step of collecting serum from saidmouse.

Clause 49. The method of clause 48, further comprising steps of

-   -   contacting said pool of humanised antibodies with said antigen;    -   binding said antigen with a humanised antibody in said pool of        humanised antibodies; and    -   isolating the humanised antibody that binds to said antigen.

Clause 50. The method of clause 49, further comprising steps of

-   -   contacting the humanised antibody that binds to said antigen        with an isotype-specific antibody, wherein the isotype-specific        antibody recognizes IgG1, IgG2a, IgG2b, or IgM; and    -   isolating the humanised antibody that binds to said        isotype-specific antibody.

Clause 51. The method of clause 48, further comprising the steps of

-   -   collecting the spleen or tissue thereof from said mouse,    -   isolating B-cells from splenic tissue,    -   fusing said B-cells with immortal myeloma cells to produce        hybridoma cells expressing a pool of humanised antibodies        comprising IgG antibodies from the serum, wherein the pool of        antibodies is used in the method of clause 48.

Clause 52. The method of any of clauses 47-51, wherein said selectedmouse comprises mouse immunoglobulin heavy chain V, D and J genesegments which are positioned in said mouse heavy chain immunoglobulinlocus in an orientation that is inverted relative to its naturalendogenous orientation.

Clause 53. The method of any of clauses 47-52 wherein the mouseexpresses Ig subtypes in a relative proportion of

-   -   (i) serum IgG1 at a concentration of about 25-350 μg/ml;    -   (ii) serum IgG2a at a concentration of about 0-200 μg/ml;    -   (iii) serum IgG2b at a concentration of about 30-800 μg/ml; and    -   (iv) serum IgM at a concentration of about 50-300 μg/ml;    -   Or    -   (i) serum IgG1 at a concentration of about 10-600 μg/ml;    -   (ii) serum IgG2a at a concentration of about 0-500 μg/ml;    -   (iii) serum IgG2b at a concentration of about 20-700 μg/ml; and    -   (iv) serum IgM at a concentration of about 50-700 μg/ml;

as determined by immunoglobulin capture on a plate followed byincubation with an anti-mouse isotype-specific antibodies eachcomprising a label and quantification of each immunoglobulin based onthe level of each label.

Clause 54. The method of any one of clauses 47 to 53, wherein, at least95, 96, 97, 98, 99, or 99.5% of the immunoglobulin heavy chainsexpressed by the mouse are immunoglobulin heavy chains comprising humanvariable regions.

Clause 55. The method of any clauses 47-54, wherein a mouseimmunoglobulin heavy chain enhancer is positioned in said mouse heavychain immunoglobulin locus between the human VH, DH, and JH genesegments and the mouse constant region.

Clause 56. The method of any of clauses 47-55, wherein a mouse S-muswitch is positioned in said mouse heavy chain immunoglobulin locusbetween the human VH, DH, and JH gene segments and the mouse constantregion.

Clause 57. The method of any of clauses 47-56, wherein endogenous mouseimmunoglobulin heavy chain V, D and J gene segments are positioned insaid mouse heavy chain immunoglobulin locus upstream to the human VH,DH, and JH gene segments.

Clause 58. The method of clause 57, wherein the mouse immunoglobulinheavy chain V, D and J gene segments are present in said mouse heavychain immunoglobulin locus with endogenous inter-gene segment sequences.

Clause 59. The method of clause 57 or 58, wherein the mouseimmunoglobulin heavy chain V, D and J gene segments are positioned insaid mouse heavy chain immunoglobulin locus in an orientation that isinverted relative to its natural endogenous orientation.

Clause 60. The method of any of clauses 47-59, wherein the mouseexpresses light chains containing human kappa variable regions.

Clause 61. The method of clause 60, wherein the mouse expressesimmunoglobulin light chains containing human Jκ.

Clause 62. The method of any of clauses 47-51, wherein the mouseexpresses light chains containing human lambda variable regions.

Clause 63. The method of clause 62, wherein the mouse expressesimmunoglobulin light chains containing human Jλ.

Clause 64. The method of clause 61, comprising a genome that includeshuman Vκ and Jκ gene segments positioned in said mouse heavy chainimmunoglobulin locus upstream to a mouse CL.

Clause 65. The mouse of clause 64, wherein the mouse CL is an endogenousCκ.

Clause 66. The mouse of clauses 64 or 65, wherein the human Vκ and Jκgene segments comprise Vκ2-24, Vκ3-20, Vκ1-17, Vκ1-16, Vκ3-15, Vκ1-13,Vκ1-12, Vκ3-11, Vκ1-9, Vκ1-8, Vκ1-6, Vκ1-5, Vκ5-2, Vκ4-1, Jκ1, Jκ2, Jκ3,Jκ4 and Jκ5.

Clause 67. The method of any of clauses 47-51, wherein the human VH, DHand JH gene segments contain

-   -   human VH gene segments: VH2-5, 7-4-1, 4-4, 1-3, 1-2, 6-1;    -   human DH gene segments: D1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 1-7, 2-8,        3-9, 5-12, 6-13, 2-15, 3-16, 4-17, 6-19, 1-20, 2-21, 3-22, 6-25,        1-26 and 7-27; and    -   human JH gene segments: J1, J2, J3, J4, J5 and J6.

The invention also includes the following Attributes:

Attribute 1. An isolated non-human vertebrate, optionally a mammal, cellwhose genome comprises an Ig H chain locus, the locus comprising, in 5′to 3′ transcriptional orientation, a V region, a J region, a D region, arat switch sequence, and a C region, wherein the C region is not a rat Cregion.

Attribute 1a. An isolated non-human vertebrate, optionally a mammal,cell whose genome comprises an Ig H chain locus, the locus comprising,in 5′ to 3′ transcriptional orientation, a V region, a J region, a Dregion, a rat switch sequence,

-   -   wherein the locus comprises a human-rat and/or a mouse-rat        sequence junction, and    -   wherein the rat sequence is provided by the rat switch sequence.

Attribute 2. An isolated non-human vertebrate, optionally a mammal, cellwhose genome comprises an Ig H chain locus, the locus comprising, in 5′to 3′ transcriptional orientation, a V region, a J region, a D region, arat switch sequence, and a C region, wherein the rat switch sequence isa rat S-mu sequence that comprises at least 3 contiguous repeats of therepeat sequence GGGCT (SEQ ID No. 46-50).

Attribute 3. An isolated non-human vertebrate, optionally a mammal, cellwhose genome comprises an Ig H chain locus, the locus comprising, in 5′to 3′ transcriptional orientation, a V region, a J region, a D region, arat switch sequence and a C region, wherein the rat switch is a rat S-musequence that comprises GAGCT (296 repeats), GGGGT (50 repeats), and/orGGGCT (83 repeats).

Attribute 4. A non-human vertebrate organism, optionally a mammal, whosegenome comprises an Ig H chain locus, the locus comprising, in 5′ to 3′transcriptional orientation, a V region, a J region, a D region, a ratswitch sequence, and a C region, wherein the C region is not a rat Cregion.

Attribute 4a. An non-human vertebrate organism, optionally a mammal,whose genome comprises an Ig H chain locus, the locus comprising, in 5′to 3′ transcriptional orientation, a V region, a J region, a D region, arat switch sequence,

-   -   wherein the locus comprises a human-rat and/or a mouse-rat        sequence junction, and    -   wherein the rat sequence is provided by the rat switch sequence.

Attribute 5. A non-human vertebrate organism, optionally a mammal, whosegenome comprises an Ig H chain locus, the locus comprising, in 5′ to 3′transcriptional orientation, a V region, a J region, a D region, a ratswitch sequence and a C region, wherein the rat switch sequence is a ratS-mu sequence that comprises at least 3 contiguous repeats of the repeatsequence GGGCT (SEQ ID NO. 46-50).

Attribute 6. A non-human vertebrate organism, optionally a mammal, whosegenome comprises an Ig H chain locus, the locus comprising, in 5′ to 3′transcriptional orientation, a V region, a J region, a D region, a ratswitch sequence and a C region, wherein the rat switch sequence is a ratS-mu sequence that comprises GAGCT (296 repeats), GGGGT (50 repeats),and/or GGGCT (83 repeats).

Attribute 7. An isolated non-human vertebrate cell or organism,optionally a mammal, whose genome comprises an Ig H chain locuscomprising DNA sequences from three or more vertebrate species, the Ig Hchain locus comprising in 5′ to 3′ transcriptional orientation at leasta V region, a D region, a J region, an enhancer, a rat switch sequence,and a C region.

Attribute 8. The non-human vertebrate cell or organism of any ofattributes 1 to 7, wherein the genome of the cell or organism furthercomprises an Ig L chain locus comprising DNA sequences from three ormore vertebrate species and wherein the Ig L chain locus comprises in 5′to 3′ transcriptional orientation at least a human V region, a human Jregion, and a C region.

Attribute 9. The non-human vertebrate cell or organism of attribute 7 or8, wherein said three or more vertebrate species are mouse, human andrat.

Attribute 10. The non-human vertebrate cell or organism of any ofattributes 1 to 9, wherein said C region is endogenous to the cell ororganism, and said V, D and/or J regions are human.

Attribute 11. The non-human vertebrate cell or organism of any ofattributes 1-10, wherein the Ig H chain locus comprises a plurality of Vregions, one or more D regions, and one or more J regions and/or whereinthe Ig L chain locus comprises a plurality of V regions and one or moreJ regions.

Attribute 12. The non-human vertebrate cell or organism of any ofattributes 1-11, wherein said V region is or said plurality of V regionsare human.

Attribute 13. The non-human vertebrate cell or organism of any ofattributes 1-11, wherein said D region is or said one or more D regionsare human.

Attribute 14. The non-human vertebrate cell or organism of any ofattributes 1-11, wherein said J region is or said one or more J regionsare human.

Attribute 15. The non-human vertebrate cell or organism of any ofattributes 11-14, wherein said V region is or said plurality of Vregions are human, said D region is or said one or more D regions arehuman, and said J region is or said one or more J regions are human.

Attribute 16. The non-human vertebrate cell or organism of any ofattributes 1, 1a, 4a, 4, 7-11 and 15, wherein said rat switch sequenceis rat S-mu.

Attribute 17. The non-human vertebrate cell or organism of any ofattributes 1, 4, 7-11, and 15 further comprising a mouse enhancersequence positioned upstream of and operatively associated with said ratswitch sequence.

Attribute 18. The non-human vertebrate cell or organism of attribute 16,further comprising a mouse enhancer sequence positioned upstream of andoperatively associated with said rat S-mu sequence.

Attribute 19. The non-human vertebrate cell or organism of any ofattributes 1-4, 7-15, wherein the C region is one of a mouse C region ora human C region.

Attribute 20. The non-human vertebrate cell or organism of attribute 19,wherein the C region is CH1.

Attribute 21. The non-human vertebrate cell or organism of attribute 19,wherein the mouse C region is one or more of a C-mu or a C-gamma.

Attribute 22. The non-human vertebrate cell or organism of attribute 21,wherein the mouse C region is a C-mu and a C-gamma.

Attribute 23. The non-human vertebrate cell or organism of attribute 7,wherein the cell is a mouse cell or the vertebrate is a mouse andwherein the mouse C region is the endogenous mouse C region.

Attribute 24. The non-human vertebrate cell or organism of any ofattributes 1, 1a, 4, 4a, and 7, wherein the rat S-mu sequence comprisesat least 3 and up to 83 contiguous repeats of the repeat sequence GGGCT(SEQ ID NO. 46-50).

Attribute 25. The non-human vertebrate cell or organism of any ofattributes 1, 1a, 2, 4, 4a, 5 and 7, comprising a rat S-mu sequencewhich comprises 296 repeats of the motif GAGCT.

Attribute 26. The non-human vertebrate cell or organism of any ofattributes 1, 1a, 2, 4, 4a, 5 and 7, comprising a rat S-mu sequencewhich comprises 50 repeats of the motif GGGGT.

Attribute 27. The non-human vertebrate cell or organism of any ofattributes 1, 1a, 2, 4, 4a, 5 and 7, comprising a rat S-mu sequencewhich comprises 83 repeats of the motif GGGCT.

Attribute 28. The non-human vertebrate cell or organism of any precedingattributes wherein the rat S-mu sequence comprises SEQ ID NO 1.

Attribute 29. The non-human vertebrate cell of any preceding attribute,wherein the cell is an ES cell, hematopoietic stem cell or hybridoma.

Attribute 30. The non-human vertebrate cell or organism of any precedingattribute, wherein the cell or organism is a mouse ES cell or a mouse,respectively.

Attribute 31. The non-human vertebrate cell or organism of any ofattributes 1-10, wherein said Ig H chain locus comprises a human JH, ahuman DH, and human VH2-5 operatively associated with a rat S-musequence

Attribute 32. The non-human vertebrate cell or organism of any ofattributes 1-10, wherein said Ig H chain locus comprises human JH1-5, ahuman DH, and a human operatively associated with a rat S-mu sequence.

Attribute 33. The non-human vertebrate cell or organism of any ofattributes 1-10, wherein said cell is a mouse cell or said organism is amouse;

-   -   wherein said Ig H chain locus comprises a mouse enhancer        positioned upstream of and operatively associated with a rat        switch sequence which is rat S-mu and    -   wherein said C region is a mouse constant region.

Attribute 34. The non-human vertebrate cell or organism of attribute 33,wherein said Ig H chain V, D and J regions are human and/or said Ig Lchain V and J regions are human.

Attribute 35. The non-human vertebrate cell or organism of attributes1-10, wherein said Ig H chain locus comprises a rearranged VDJ region.

Attribute 36. The non-human vertebrate cell or organism of attribute 35,wherein said rearranged VDJ region is human.

Attribute 37. The non-human vertebrate cell or organism of any ofattributes 1-10, wherein the cell or organism comprises a genomecomprises human DNA comprising a plurality of human IgH V regions, oneor more human D regions and one or more human J regions upstream of thehost non-human mammal constant region and wherein the human IgH VDJregion comprises nucleotides 105,400,051 to 106,368,585 from humanchromosome 14 (co-ordinates refer to NCBI36 for the human genome,ENSEMBL Release 54), or an equivalent human region from another human.

Attribute 38. The non-human vertebrate cell or organism of attribute 37,wherein human DNA is positioned between a non-human mammalian constantregion and a non-human mammal J region positioned 3′ distal to any othernon-human J region.

Attribute 39. The non-human vertebrate cell or organism according toattribute 37, when the cell is a mouse cell or the organism is a mousesaid V, D and J regions are human and positioned between coordinates114,667,091 and 114,665,190 of mouse chromosome 12 (coordinates refer toNCBI m37, for the mouse C57BL/6J strain), or at an equivalent positionin another non-human mammal genome.

Attribute 40. The non-human vertebrate cell or organism of attribute 39,when the cell is a mouse cell or the organism is a mouse said V, D and Jregions are human and positioned between coordinates 114,667,089 and114,667,090 (co-ordinates refer to NCBI m37, for the mouse C57BL/6Jstrain), or at an equivalent position in another non-human mammalgenome.

Attribute 41. The non-human vertebrate cell or organism of attribute 37,wherein the cell is a mouse cell or the organism is a mouse, and whereinsaid V, D and J regions are human and positioned between coordinates114,666,183 and 114,666,725, such as between coordinates 114,666,283 and114,666,625, optionally between coordinates 114,666,335 and 114,666,536,optionally between coordinates 114,666,385 and 114,666,486, optionallybetween coordinates 114,666,425 and 114,666,446, such as betweencoordinates 114,666,435 and 114,666,436 of mouse chromosome 12, withreference to NCBI m37 for the mouse genome relating to mouse strainC57BL/6J or an equivalent position of mouse chromosome 12 from adifferent mouse strain or an equivalent position in the genome ofanother non-human vertebrate.

Attribute 42. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein the cell is a mouse cell or the organism isa mouse and wherein said Ig H chain V, D and J regions or said Ig Lchain V and J regions are human.

Attribute 43. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein said V, D and J regions are human andcomprise or consist of nucleotides 106,328,851-107,268,544, such asnucleotides 106,328,901-107,268,494, such as nucleotides106,328,941-107,268,454, such as nucleotides 106,328,951-107,268,444 ofhuman Chromosome 14, with reference to the GRCH37/hg19 sequencedatabase, or equivalent nucleotides relating to chromosome 14 from adifferent human sequence or database.

Attribute 44. The non-human vertebrate cell or organism according to anyof attributes 1-10, comprising a human kappa VJ region DNA comprising,in germline configuration, all of the V and J regions and interveningsequences from a human.

Attribute 45. The non-human vertebrate cell or organism according toattribute 44, wherein the human kappa VJ region DNA is positionedbetween coordinates 70,673,918-70,675,517, such as between coordinates70,674,418-70675,017, such as between coordinates 70,674, 65570,674,856, such as between coordinates 70,674, 705-70,674,906, such asbetween coordinates 70,674, 745-70,674,766, such as between coordinates70,674,755 and 70,674,756 of mouse chromosome 6 (with reference to NCBIm37 for the mouse genome, relating to mouse strain C57BL/6J), or at anequivalent position in another genome.

Attribute 46. The non-human vertebrate cell or organism according toattribute 45, wherein the human kappa VJ region DNA comprises orconsists of a fragment from human chromosome 2, numbered with referenceto the GRCH37/hg19 sequence database, or equivalent nucleotides relatingto chromosome 2 from a different human sequence or database, thefragment selected from 1 or more of: (i) nucleotides89,158,979-89,630,537, such as 89,159,029-89,630,487, such as89,159,069-89,630,447, such as 89,159,079-89,630,437, optionally inaddition to fragment (ii); (ii) nucleotides 89,941,614-90,267,076, suchas 89,941,664-90,267,026, such as 89, 941,704-90,266,986, such as89,941,714-90,266,976; optionally in addition to fragment (i); and (iii)nucleotides 89,158,979-90,267, 076, such as nucleotides89,159,079-90,266,976.

Attribute 47. The non-human vertebrate cell or organism according to anyof attributes 1-10, comprising human lambda region DNA which comprisesat least one human Jλ region and at least one human Cλ region,optionally Cλ6 and/or Cλ7.

Attribute 48. The non-human vertebrate cell or organism according toattribute 47, comprising a plurality of human Jλ regions, optionally twoor more of Jλ1, Jλ2, Jλ6 and Jλ7, optionally all of Jλ1, Jλ2, Jλ6 andJλ7.

Attribute 49. The non-human vertebrate cell or organism according toattribute 47, comprising at least one human Jλ-Cλ cluster, optionally atleast Jλ7-Cλ7.

Attribute 50. The non-human vertebrate cell or organism according to anyof attributes 1-10, comprising a human Eλ enhancer.

Attribute 51. The non-human vertebrate cell or organism according to anyof attributes 1-10, comprising human lambda VJ region DNA whichcomprises, in germline configuration, all of the V and J regions andintervening sequences from a human.

Attribute 52. The non-human vertebrate cell or organism according toattribute 51, wherein the human lambda VJ region DNA comprises orconsists of nucleotides 22,375,509-23,327,984, such as nucleotides22,375,559-23,327,934, such as nucleotides 22,375,599-23,327,894, suchas nucleotides 22,375,609-23,327,884 from human chromosome 22, withreference to the GRCH37/hg19 sequence database, or equivalentnucleotides relating to human chromosome 22 from a different humansequence or database.

Attribute 53. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein non-mouse DNA is positioned in the mousegenome between co-ordinates 19,027,763 and 19,061,845, such as betweenco-ordinates 19,037,763 and 19,051,845, such as between co-ordinates19,047,451 and 19,047,652, such as between co-ordinates 19,047,491 and19,047,602, such as between co-ordinates 19,047,541 and 19,047,562, suchas between co-ordinates 19,047,551 and 19,047,552 of mouse chromosome16, with reference to NCBI m37 for the mouse genome, or at an equivalentposition in other genome.

Attribute 54. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein non-human DNA is positioned in the mousegenome between co-ordinates 70,673,918 and 70,675,517 such as betweenco-ordinates 70,674,418 and 70,675,017, such as between co-ordinates70,674,655 and 70,674,856, such as between co-ordinates 70,674,705 and70,674,806, such as between co-ordinates 70,674,745 and 70,674,766, suchas between co-ordinates 70,674,755 and 70,674,756 of mouse chromosome 6,with reference to NCBI m37 for the mouse genome, relating to mousestrain C57BL/6J) or at an equivalent position in another genome.

Attribute 55. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein said V, D and J regions are human and humanlight chain kappa VJC DNA, or part thereof, is inserted immediatelyupstream of the mouse kappa VJC region.

Attribute 56. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein the genome of the cell or organism ismodified to prevent or reduce expression of fully host-species specificantibodies.

Attribute 57. The non-human vertebrate cell or organism according toattribute 56, wherein the genome of the cell or organism is modified byinversion of all or part of the non-human mammal VDJ region, or VJregion.

Attribute 58. The non-human vertebrate cell or organism according toattribute 56, wherein the genome of the cell or organism comprises humanDNA and non-human DNA, and said non-human DNA comprises endogenous V andJ regions or V, D, and J regions which have not been deleted.

Attribute 59. The non-human vertebrate organism according to any ofattributes 1-10 generated in a genetic background which prevents theproduction of mature host B and T lymphocytes.

Attribute 60. The non-human vertebrate organism according to attribute59 generated in a Rag-1 or Rag-2 deficient background.

Attribute 61. The non-human vertebrate cell according to attribute 29which is an ES cell or hematopoietic stem cell capable of developinginto a non-human mammal able to produce a repertoire of antibodies orantibody chains which are chimaeric, said chimaeric antibodies or chainshaving a non-human mammal constant region and a human variable region.

Attribute 62. The non-human vertebrate cell according to attribute 29which is an ES cell or hematopoietic stem cell capable of contributingto tissues and organs of a non-human mammal which is able to produce arepertoire of antibodies or antibody chains which are chimaeric, saidchimaeric antibodies or chains having a non-human mammal constant regionand a human variable region.

Attribute 63. The non-human vertebrate cell or organism according to anyof attributes 1-10, comprising human variable region DNA from at least ahuman heavy and human light chain.

Attribute 64. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein the cell or organism is homozygous at one,two or all three immunoglobulin loci for DNA encoding a chimaericantibody chain.

Attribute 65. The non-human vertebrate cell or organism according to anyof attributes 1-10, wherein the cell or organism is heterozygous at one,two or all three immunoglobulin loci for DNA encoding a chimaeric heavyor light chain.

Attribute 66. The non-human vertebrate cell or organism according toattributes 1-10, wherein the genome of the cell or organism does notcomprise constant region DNA from another cell or organism.

Attribute 67. The non-human vertebrate cell according to attribute 29which is immortalised.

Attribute 68. The non-human vertebrate cell according to attribute 67which is an ES cell line AB2.1, or a cell from a mouse strain selectedfrom C57BL/6, M129, 129/SV, BALB/c, and any hybrid of C57BL/6, M129,129/SV or BALB/c.

Attribute 69. A method for obtaining immunoglobulin heavy chaincomprising human immunoglobulin variable region,

-   -   comprising providing the mouse of any of attributes attribute        1a, 4, 4a, 5-28, 30-60, and 63-66 and    -   isolating polypeptide comprising immunoglobulin heavy chain        comprising said human variable region.

Attribute 69a. The method of attribute 69, wherein said immunoglobulinheavy chain is a heavy chain of two chain or four chain antibody.

Attribute 69b. An antibody isolated according to the method of attribute69.

Attribute 69c. A pharmaceutical composition comprising the antibody ofattribute 69b and a pharmaceutically acceptable carrier, excipient, ordiluent.

Attribute 69d. The method of attribute 69 or 69a, wherein a step ofimmunizing the mouse with an antigen is performed before the step ofisolating the immunoglobulin heavy chains.

Attribute 69e. The method of attribute 69d, wherein the antigen is ahuman antigen.

Attribute 69f. The method of attribute 69 or 69a, wherein saidimmunoglobulin heavy chain is one of isotype IgG1, IgG2, IgG3, and IgMsaid human variable region specifically binds said antigen.

Attribute 69g. The method of attribute 69f, wherein said immunoglobulinheavy chain is a heavy chain of a two chain or four chain antibody andsaid antibody specifically binds said antigen.

Attribute 70. A polynucleotide landing pad sequence, the polynucleotidecomprising nucleic acid regions homologous to regions of a targetchromosome to allow for insertion by homologous recombination into thetarget chromosome, and comprising a nucleic acid site which permitsrecombinase-driven insertion of a nucleic acid into the landing pad,wherein the polynucleotide sequence comprises one or more of: (i) a ratswitch sequence, optionally a rat S-mu switch, which is optionally thesequence of SEQ ID NO 1; (ii) in a 5′ to 3′ direction, a mouse Eμsequence, a rat switch sequence, and mouse Cμ; and/or (iii) a 3′homology arm having the sequence of SEQ ID NO 6.

Attribute 71. The non-human vertebrate organism, optionally a mammal,comprising a landing pad sequence according to attribute 70 which hasbeen inserted into the genome of the cell.

Attribute 72. The non-human vertebrate cell or organism, optionally amammal, or landing pad according to attribute 70 or 71, wherein the ratswitch sequence comprises 3, 4, 5, 6 or more contiguous repeats of thesequence GGGCT, optionally being SEQ ID NO 1.

Attribute 73. The non-human vertebrate cell or organism, optionally amammal, or landing pad according to any of attributes 70 to 72, whereinthe landing pad sequence comprises the sequence of SEQ ID NO 2.

Attribute 74. The non-human vertebrate cell or organism, optionally amammal, or landing pad according to any of attributes 70 to 73, whereinthe landing pad sequence comprises the sequence of SEQ ID NO 3.

Attribute 75. A method for producing an isolated non-human vertebrate,optionally a mammal, cell comprising:

-   -   inserting one or more non-native DNA constructs into a non-human        mammal cell genome,    -   thereby producing a cell whose genome includes an Ig H chain        locus having a V region, a J region, a D region, a rat switch        sequence, and a C region in a 5′ to 3′ transcriptional        orientation, wherein the C region is not a rat C region.

Attribute 76. A method for producing an isolated non-human vertebrate,optionally a mammal, cell comprising:

-   -   inserting one or more non-native DNA constructs into a non-human        mammal cell genome,    -   thereby producing a cell whose genome includes an Ig H chain        locus having a V region, a J region, a D region, a rat switch        sequence, and a C region in a 5′ to 3′ transcriptional        orientation, wherein the rat switch sequence is a rat S-mu        sequence that comprises at least 3 contiguous repeats of the        repeat sequence GGGCT (SEQ ID NO. 46-50).

Attribute 77. A method for producing a non-human vertebrate, optionallya mammal, cell comprising:

-   -   inserting one or more non-native DNA constructs into a non-human        mammal cell genome,    -   thereby producing a cell whose genome includes an Ig H chain        locus having a V region, a J region, a D region, a rat switch        sequence, and a C region in a 5′ to 3′ transcriptional        orientation, wherein the rat switch is a rat S-mu sequence that        comprises GAGCT (296 repeats), GGGGT (50 repeats), and/or GGGCT        (83 repeats).

Attribute 78. A method for producing a non-human vertebrate organism,optionally a mammal, comprising:

-   -   inserting one or more non-native DNA constructs into a non-human        mammal cell genome,    -   thereby producing a genome including an Ig H chain locus having        a V region, a J region, a D region, a rat switch sequence, and a        C region in a 5′ to 3′ transcriptional orientation, wherein the        C region is not a rat C region.

Attribute 79. A method for producing a non-human vertebrate organism,optionally a mammal, comprising:

-   -   inserting one or more non-native DNA constructs into a non-human        mammal cell genome,    -   thereby producing a genome including an Ig H chain locus having        a V region, a J region, a D region, a rat switch sequence, and a        C region in a 5′ to 3′ transcriptional orientation, wherein the        rat switch is a rat S-mu sequence that comprises at least 3        contiguous repeats of the repeat sequence GGGCT (SEQ ID NO.        46-50).

Attribute 80. A method for producing a non-human vertebrate organism,optionally a mammal, comprising:

-   -   inserting one or more non-native DNA constructs into a non-human        mammal cell genome,    -   thereby producing a genome including an Ig H chain locus having        a V region, a J region, a D region, a rat switch sequence, and a        C region in a 5′ to 3′ transcriptional orientation wherein the        rat switch is a rat S-mu sequence that comprises GAGCT (296        repeats), GGGGT (50 repeats), and/or GGGCT (83 repeats).

Attribute 81. A method for producing an isolated non-human vertebratecell or organism, optionally a mammal, comprising:

-   -   inserting one or more non-native DNA constructs into a non-human        mammal cell genome,    -   thereby producing a genome including an Ig H chain locus having        DNA from three or more mammalian species, wherein the Ig H chain        locus includes, in a 5′ to 3′ transcriptional orientation, at        least a V region, a D region, a J region, an enhancer, a rat        switch sequence, and a C region.

Attribute 82. The method of any of attributes 75 to 81, furthercomprising:

-   -   inserting one or more non-native DNA constructs into the        non-human mammal cell genome,    -   thereby producing a genome including an Ig L chain locus        comprising in 5′ to 3′ transcriptional orientation at least a        human VL region, a human JL region, and a CL region.

Attribute 83. The method attribute 81 or 82, wherein said constantregion (CL) is a mouse or human constant region.

Attribute 84. The method of attribute 81 or 82, wherein the enhancer isa mouse enhancer sequence.

Attribute 85. The method of any of attributes 75, 78, or 81-84, whereinsaid rat switch sequence is rat S-mu.

Attribute 86. The method of any of attributes 75 to 85, wherein said V,D and/or J region is human or V and/or J region is human.

Attribute 87. The method of any of attributes 75 to 86, wherein the IgHlocus C region is one of a mouse C region or a human C region.

Attribute 88. The method according to any of attributes 75 to 87,wherein the non-human mammal cell genome is then modified to preventexpression of native (fully host species specific) antibodies in thecell or vertebrate organism, optionally by inversion of all or part ofhost non-human mammal Ig locus, optionally by insertion of one or moresite specific recombinase sites into the genome and then use of thesesites in recombinase-mediated excision or inversion of all or a part ofthe host non-human mammal Ig locus.

Attribute 89. The method according to any of attributes 75 to 88,wherein the cell is an ES cell.

Attribute 90. The method according to any of attributes 75 to 89,wherein the step of inserting DNA is accomplished by step-wise insertionof multiple constructs by homologous recombination and wherein said DNAis inserted upstream of the host non-human mammal constant region.

Attribute 91. The method according to any of attributes 75 to 90,wherein the step of inserting DNA occurs at a site where an initiationcassette has been inserted into the genome of an ES cell, therebyproviding a unique targeting region.

Attribute 92. The method according to any of attributes 75 to 91,wherein one or more insertion events utilises site specificrecombination.

Attribute 93. The method according to attribute 92, wherein said one ormore insertion events is mediated by, or involves, one or more of Frtsites, Flp recombinase, Dre recombinase, Rox sites, or PhiC31recombinase.

Attribute 94. The method according to any of attributes 75 to 93,wherein inserting one or more non-native DNA constructs into a non-humanmammal cell genome comprises the steps of:

-   -   1 insertion of DNA forming an initiation cassette (also called a        landing pad herein) into the genome of a cell;    -   2 insertion of a first DNA fragment into the insertion site, the        first DNA fragment comprising a first portion of a human DNA and        a first vector portion containing a first selectable marker or        generating a selectable marker upon insertion;    -   3 optionally removal of part of the vector DNA;    -   4 insertion of a second DNA fragment into the vector portion of        the first DNA fragment, the second DNA fragment containing a        second portion of human DNA and a second vector portion, the        second vector portion containing a second selectable marker, or        generating a second selectable marker upon insertion;    -   5 removal of any vector DNA to allow the first and second human        DNA fragments to form a contiguous sequence; and    -   6 iteration of the steps of insertion of a part of the human        V(D)J DNA and vector DNA removal, as necessary, to produce a        cell with all or part of the human VDJ or VJ region sufficient        to be capable of generating a chimaeric antibody in conjunction        with a host constant region,    -   wherein the insertion of at least one DNA fragment uses site        specific recombination.

Attribute 95. The method according to any of attributes 75 to 94,wherein the landing pad sequence comprises SEQ ID NO 6, SEQ ID NO. 2, orSEQ ID NO. 3.

Attribute 96. The method according to any of attributes 75 to 95,wherein the landing pad is inserted into the mouse cell genome byhomologous recombination between mouse J1-4 and mouse C mu sequences.

Attribute 97. The method according to any of attributes 75 to 96,wherein the landing pad is recombined into the mouse cell genome byhomologous recombination between mouse J1-4 and E mu sequences.

Attribute 98. The method according to any of attributes 75 to 97,wherein the landing pad comprises a non-host S-mu, such as a rat S-muswitch.

Attribute 99. The method, cell or mammal as attributed in any ofattributes 1 to 98, wherein a human coding region DNA sequence is in afunctional arrangement with a non-human mammal control sequence, suchthat transcription of the human DNA is controlled by the non-humanmammal control sequence.

Attribute 100. A method for producing an antibody or antibody heavy orlight chain specific to a desired antigen, the method comprisingimmunizing the non-human vertebrate as attributed in attribute 4-28,30-60, 63-66, or 71-74 with the desired antigen and recovering theantibody or antibody chain or recovering a cell producing the antibodyor heavy or light chain.

Attribute 101. The method for producing a fully humanised antibody orantibody chain comprising carrying out the method according to attribute100 and then replacing the non-human mammal constant region of therecovered antibody or antibody chain with a human constant region,suitably by engineering of the nucleic acid encoding the antibody orantibody chain.

Attribute 102. A humanised antibody or antibody chain produced accordingto attribute 100 or 101 or a derivative thereof that binds the desiredantigen.

Attribute 103. Use of the humanised antibody or chain produced accordingto attribute 100 or 101 or a derivative thereof that binds the desiredantigen in medicine.

Attribute 104. The humanised antibody or antibody chain producedaccording to attribute 100 or 101 or a derivative thereof that binds thedesired antigen for use in medicine.

Attribute 105. A pharmaceutical composition comprising an antibody orantibody chain according to attribute 100 or 101 or a derivative thereofthat binds the desired antigen and a pharmaceutically acceptable carrieror other excipient.

Attribute 106. A chimaeric antibody derivative of a chimaeric antibodyproduced according to attribute 100, wherein the derivative binds thedesired antigen.

Attribute 107. A mouse whose genome comprises an insertion of human IgHVDJ DNA between co-ordinates 114,667,090 and 114,665,190 of mousechromosome 12, such as between co-ordinates 114,667,089 and 114,667,090,the insert comprising nucleotides 105,400,051 to 106,368,585 from humanchromosome 14 (co-ordinates refer to NCBI36 for the human genome andNCBI m37, for the mouse C57BL/6J strain, or equivalent coordinates inanother human chromosome 14 sequence or in another mouse genomerespectively), the insertion being upstream of the host non-human mammalconstant region such that the mouse is able to produce a repertoire ofchimaeric heavy chains having a non-human mammal constant region and ahuman variable region, wherein the mammal also comprises an insertion ofthe complete VJC human light chain region such that a fully human lambdaor kappa human antibody chain may be generated which is able to form anantibody with a chimaeric heavy chain.

Attribute 108. A mouse whose genome comprises an insertion of human IgHVDJ DNA between co-ordinates 114,667,090 and 114,667,091 of mousechromosome 12, the insert comprising or consisting of nucleotides105,400,051 to 106,368,585 from human chromosome 14 (co-ordinates referto NCBI36 for the human genome and NCBI m37 for the mouse C57BL/6Jstrain, or equivalent coordinates in another human chromosome 14sequence or in another mouse genome respectively), the insertion beingupstream of the mouse constant region such that the mouse is able toproduce a repertoire of chimaeric heavy chains having a mouse constantregion and a human variable region, wherein the mouse also comprises aninsertion of the complete VJC human light chain region such that a fullyhuman lambda or kappa human antibody chain may be generated which isable to form an antibody with a chimaeric heavy chain.

Attribute 109. A mouse whose genome comprises an insertion of human IgHVDJ DNA between co-ordinates 114,667,090 and 114,665,190 of mousechromosome 12, where co-ordinates refer to NCBI m37, for the mouseC57BL/6J strain, or an insertion at an equivalent position in anothermouse strain, the insert comprising or consisting of nucleotides106,328,951-107,268,444 from human chromosome 14, where co-ordinatesrefer to the GRCH37/hg19 sequence database for humans, or the samenucleotides from an equivalent position in another human chromosome 14sequence, the insertion being upstream of the host mouse constant regionsuch that the mouse is able to produce a repertoire of chimaeric heavychains having a mouse constant region and a human variable region,wherein the mouse also comprises an insertion of the complete VJC humanlight chain region which is functional to generate a fully human lambdaor kappa human antibody chain which forms an antibody with a chimaericheavy chain.

Attribute 110. A mouse according to attribute 109, wherein the insertionis between co-ordinates 114,666,435 and 114,666,436 of mouse chromosome12.

Attribute 116. A method of making a non-human vertebrate cell,optionally a mouse or rat, the method comprising:

-   -   (a) providing the non-human ES cell of attribute 29, 61, 62, or        68 and whereby the non-human ES cell is capable of giving rise        to a progeny cell in which endogenous antibody expression is        inactivated and wherein the progeny cell is capable of        expressing antibodies comprising human variable regions; and    -   (b) optionally differentiating said non-human ES cell into said        progeny cell or a non-human vertebrate organism comprising said        progeny cell.

Attribute 117. The method according to attribute 116, wherein saidplurality of human antibody gene segments comprises at least elevenhuman V segments.

Attribute 118. The method according to attribute 116 or 117, whereinsaid plurality of human antibody gene segments comprises at least sixhuman J segments.

Attribute 119. The method according to any one of attributes 116 to 118,wherein a human nucleotide sequence is inserted in step (b), thenucleotide sequence comprising said antibody gene segments, wherein thenucleotide sequence is at least 110 kb.

Attribute 120. The method according to any one of attributes 116 to 119,wherein the endogenous locus is a heavy chain locus and the humanantibody gene segments are between the 3′-most endogenous JH genesegment and endogenous C-mu.

Attribute 121. The method according to any one of attributes 116 to 120,wherein the progeny cell is homozygous for said transgenic locus.

Attribute 122. A method of isolating an antibody that binds apredetermined antigen, the method comprising

-   -   (a) providing a vertebrate organism, mouse, or mammal,        optionally a rat, according to any one of attributes 1a, 4, 4a,        5-28, 30-60, 63-66, or 71-74, and 107-110;    -   (b) immunising said vertebrate organism, mouse, or mammal with        said antigen (optionally wherein the antigen is an antigen of an        infectious disease pathogen);    -   (c) removing B lymphocytes from the vertebrate organism, mouse,        or mammal and selecting one or more B lymphocytes expressing        antibodies that bind to the antigen;    -   (d) optionally immortalising said selected B lymphocytes or        progeny thereof, optionally by producing hybridomas therefrom;        and    -   (e) isolating an antibody (e.g., and IgG-type antibody)        expressed by the B lymphocytes.

Attribute 123. The method of attribute 122, comprising the step ofisolating from said B lymphocytes nucleic acid encoding said antibodythat binds said antigen; optionally exchanging the heavy chain constantregion nucleotide sequence of the antibody with a nucleotide sequenceencoding a human or humanised heavy chain constant region and optionallyaffinity maturing the variable region of said antibody; and optionallyinserting said nucleic acid into an expression vector and optionally ahost.

Attribute 124. The method of attribute 122 or 123, further comprisingmaking a mutant or derivative of the antibody produced by the method ofattribute 122 or 123.

Attribute 125. An antibody or fragment thereof comprising variableregions that specifically bind a predetermined antigen with a sub-50 nMaffinity as determined by surface plasmon resonance, wherein theantibody is isolated from a non-human vertebrate organism, mouse, ormammal, optionally a rat, according to any one of attributes 1a, 4, 4a,5-28, 30-60, 63-66, or 71-74, and 107-110 and comprises heavy chainCDR3s (as defined by Kabat) encoded by a rearranged VDJ of saidvertebrate organism, mouse, or mammal, wherein the VDJ is the product ofrearrangement in vivo of a human JH gene segment of a heavy chain locusof said vertebrate with D (optionally a human D gene segment of saidlocus) and VH gene segments.

Attribute 126. An antibody or fragment that is identical to an antibodyof attribute 125 or a derivative thereof, optionally a derivative whoseconstant regions are human and/or an affinity matured derivative, thatspecifically binds said antigen with a sub-50 nM affinity as determinedby surface plasmon resonance.

Attribute 127. A pharmaceutical composition comprising an antibody orfragment of attribute 125 or 126 and a pharmaceutically-acceptablediluent, excipient or carrier.

Attribute 128. A nucleotide sequence encoding a heavy chain variableregion of an antibody or fragment of attribute 125 or 126, optionally aspart of a vector (e.g., an expression vector).

Attribute 129. The nucleotide sequence of attribute 128, wherein thesequence is a cDNA derived from a B-cell of the vertebrate from whichthe antibody of attribute 125 is isolated, or is identical to such acDNA.

Attribute 130. An isolated host cell (e.g., a hybridoma or a CHO cell ora HEK293 cell) comprising a nucleotide sequence according to attribute128 or 129.

Attribute 131. A method of isolating an antibody that binds apredetermined antigen, the method comprising

-   -   (a) providing a vertebrate organism, mouse, or mammal,        optionally a rat, according to any one of attributes 1a, 4, 4a,        5-28, 30-60, 63-66, or 71-74, and 107-110;    -   (b) immunising said vertebrate organism, mouse, or mammal with        said antigen;    -   (c) removing B lymphocytes from the vertebrate organism, mouse,        or mammal and selecting a B lymphocyte expressing an antibody        that binds to the antigen with sub-nM affinity, wherein the        antibody is according to attribute 125;    -   (d) optionally immortalising said selected B lymphocyte or        progeny thereof, optionally by producing hybridomas therefrom;        and    -   (e) isolating an antibody (e.g., and IgG-type antibody)        expressed by the B lymphocyte.

Attribute 132. The method of attribute 131, comprising the step ofisolating from said B lymphocyte nucleic acid encoding said antibodythat binds said antigen; optionally exchanging the heavy chain constantregion nucleotide sequence of the antibody with a nucleotide sequenceencoding a human or humanised heavy chain constant region and optionallyaffinity maturing the variable region of said antibody; and optionallyinserting said nucleic acid into an expression vector and optionally ahost.

Attribute 133. The method of attribute 131 or 132, further comprisingmaking a mutant or derivative of the antibody produced by the method ofattribute 131 or 132.

Attribute 137. A cassette for inversion and inactivation of endogenousmouse antibody heavy chain gene segments, the segments being part of aheavy chain locus sequence on chromosome 12 of a mouse cell (e.g., EScell) wherein the sequence is flanked at its 3′ end by a site-specificrecombination site (e.g., lox, rox or fit), the cassette comprising anucleotide sequence encoding an expressible label or selectable markerand a compatible site-specific recombination site (e.g., lox, rox orfit) flanked by a 5′ and a 3′ homology arm, wherein (i) the 5′ homologyarm is mouse chromosome 12 DNA from coordinate 119,753,124 to coordinate119,757,104 and the 3′ homology arm is mouse chromosome 12 DNA fromcoordinate 119,749,288 to 119,753,123; (ii) the 5′ homology arm is mousechromosome 12 DNA from coordinate 119,659,459 to coordinate 119,663,126and the 3′ homology arm is mouse chromosome 12 DNA from coordinate119,656,536 to 119,659,458; or (iii) the 5′ homology arm is mousechromosome 12 DNA from coordinate 120,918,607 to coordinate 120,921,930and the 3′ homology arm is mouse chromosome 12 DNA from coordinate120,915,475 to 120,918,606.

Attribute 138. A mouse or mouse cell whose genome comprises an inversionof a chromosome 12, wherein the inversion comprises inverted endogenousheavy chain gene segments (e.g., VH, D and JH, such as the entireendogenous heavy chain VDJ region); wherein the genome of the mouse ormouse cell comprises a transgenic heavy chain locus comprising aplurality of human VH gene segments, a plurality of human D segments anda plurality of human JH segments upstream of and operatively associatedwith an endogenous constant region (e.g., C mu) so that the mouse ormouse cell (optionally following differentiation into a B-cell) iscapable of expressing an antibody comprising a variable regioncomprising sequences derived from the human gene segments; and whereinthe inversion is (i) an inversion of mouse chromosome 12 from coordinate119,753,123 to coordinate 114,666,436; (ii) an inversion of mousechromosome 12 from coordinate 119,659,458 to coordinate 114,666,436; or(iii) an inversion of mouse chromosome 12 from coordinate 120,918,606 tocoordinate 114,666,436.

The invention also includes the following provisions:

≥80% of all LIGHT chain are human Vλ

Provision 1. A non-human vertebrate having a genome comprising arecombinant immunoglobulin light chain locus, said locus comprising atargeted insert positioned in an endogenous light chain locus,

-   -   wherein the targeted insert comprises human lambda light chain        locus DNA and is positioned upstream to a lambda light chain        constant region,    -   wherein said targeted insert includes a repertoire of human Vλ        and Jλ gene segments,    -   wherein the vertebrate expresses immunoglobulin light chains        comprising human lambda variable regions, and    -   wherein at least 80% of the immunoglobulin light chains        expressed in said vertebrate comprises human lambda variable        regions.

Provision 2. The vertebrate of provision 1, wherein the repertoire ofhuman Vλ and Jλ insertion comprises at least the functional human V andJ gene segments comprised by a human lambda chain immunoglobulin locusfrom Vλ2-18 to Cλ7.

Provision 3. The vertebrate of provision 1, wherein the endogenous lightchain locus is the endogenous kappa locus.

Provision 4. The vertebrate of provision 3, wherein the genome ishomozygous for the repertoire of human Vλ and Jλ gene segments andwherein the endogenous kappa chain expression is substantially inactive.

Provision 5. The vertebrate of provision 4, wherein the endogenous kappachain expression is completely inactive.

Provision 6. The vertebrate of provision 1, wherein the endogenous lightchain locus is the endogenous lambda locus.

Provision 7. The vertebrate of provision 6, wherein the genome ishomozygous for the repertoire of human Vλ and Jλ gene segments andwherein expression of the endogenous lambda chain is substantiallyinactive.

Provision 8. The vertebrate of provision 7, wherein expression of theendogenous lambda chain is completely inactive.

Provision 9. The vertebrate of provision 1, wherein the targeted insertis positioned downstream of endogenous V and J light chain genesegments.

Provision 10. The vertebrate of provision 1, wherein the targeted insertincludes a constant region of a human lambda light chain locus.

Provision 11. The vertebrate of provision 10, wherein said light chainsexpressed by said vertebrate comprise V-C regions derived fromrecombination of human Vλ, Jλ, and Cλ gene segments.

Provision 12. The vertebrate of provision 1, wherein the vertebrate isderived from a mouse ES cell or a rat ES cell.

Provision 13. The vertebrate of provision 1, wherein the vertebrate is amouse or a rat.

Provision 14. The vertebrate of provision 1, wherein the targeted insertcomprises inter-gene segment intervening sequences being human lambdalight chain locus DNA which is between functional human V and J lightchain gene segments in a human locus or comprises inter-gene segmentintervening sequences being lambda light chain locus DNA which isbetween corresponding lambda light chain gene segments in an endogenousnon-human vertebrate genome.

Provision 15. The vertebrate of provision 14, wherein the targetedinsert includes a human lambda immunoglobulin gene segment pseudogene.

Provision 16. The vertebrate of provision 14, wherein the targetedinsert lacks a human lambda immunoglobulin gene segment pseudogene.

Provision 17. The vertebrate of provision 1, wherein at least 70, 75,80, 84, 85, 90, 95, 96, 97, 98, or 99%, or 100% of immunoglobulin lightchains expressed by said vertebrate comprise human V regions derivedfrom recombination of human Vλ and Jλ gene segments.

Provision 18. The vertebrate of provision 17, wherein at least 90% ofimmunoglobulin light chains expressed by said vertebrate comprise humanV regions derived from recombination of human Vλ and Jλ gene segments.

≥60% of all LIGHT chains have human Vλ regions

Provision 19. A non-human vertebrate having a genome comprising arecombinant immunoglobulin light chain locus, said locus comprising atargeted insert positioned in an endogenous light chain locus,

-   -   wherein the targeted insert comprises human lambda light chain        locus DNA which is positioned upstream to a lambda light chain        constant region and includes a repertoire of human Vλ and Jλ        gene segments,    -   wherein said genome comprises kappa V gene segments positioned        upstream to a light chain constant region,    -   wherein the vertebrate expresses immunoglobulin light chains        comprising lambda variable regions, and    -   wherein at least 60% of immunoglobulin light chains expressed by        said vertebrate comprises human lambda variable regions.

Provision 20. The vertebrate provision 19, wherein at least 65, 70, 80,84, 85, 90, 95, 96, 97, 98, or 99%, or 100% of immunoglobulin lightchains expressed by said vertebrate comprises human variable regionsderived from recombination of human Vλ and Jλ gene segments.

Provision 21. The vertebrate of provision 20, wherein at least 84% ofimmunoglobulin light chains expressed by said vertebrate comprises humanvariable regions derived from recombination of human Vλ and Jλ genesegments.

Provision 22. The vertebrate of provision 21, wherein at least 95% ofimmunoglobulin light chains expressed by said vertebrate comprises humanvariable regions derived from recombination of human Vλ and Jλ genesegments.

Provision 23. The vertebrate of provision 19, wherein the vertebrate isderived from a mouse ES cell or a rat ES cell.

Provision 24. The vertebrate of provision 19, wherein the vertebrate isa mouse or a rat.

Provision 25. The vertebrate or cell of provision 19, wherein thetargeted insert is positioned downstream of endogenous V and J lightchain gene segments.

Provision 25a. The vertebrate of provisions 19, wherein the kappa V genesegments positioned upstream to a light chain constant region areendogenous kappa V gene segments.

Vλ Jλ into kappa or lambda locus

Provision 26. A non-human vertebrate or cell having a genome comprisinga recombinant immunoglobulin light chain locus, said locus comprising atargeted insert positioned downstream to endogenous V and J light chaingene segments,

-   -   wherein the targeted insert comprises human immunoglobulin Vλ        and Jλ gene segments,    -   wherein said human Vλ and Jλ gene segments are positioned        upstream to a light chain constant region,    -   wherein said human Vλ and Jλ gene segments comprise at least the        functional V and J gene segments from Vλ2-18 to Cλ7 of a human        lambda light chain locus, and    -   wherein said vertebrate or cell expresses immunoglobulin light        chains comprising human lambda variable regions.

Provision 27. The vertebrate or cell of provision 26, wherein thetargeted insert includes a constant region of a human lambda light chainlocus.

Provision 28. The vertebrate or cell of provision 27, wherein said lightchains expressed by said vertebrate or cell comprise human V-C regionsderived from recombination of human Vλ, Jλ, and Cλ gene segments.

Provision 29. The vertebrate or cell of provision 26, wherein theendogenous V and J light chain gene segments are V kappa and J kappagene segments.

Provision 30. The vertebrate or cell of provision 26, wherein endogenouskappa chain expression is substantially inactive.

Provision 31. The vertebrate or cell of provision 30, wherein theendogenous kappa chain expression is completely inactive.

Provision 32. The vertebrate or cell of provision 26, wherein theendogenous V and J light chain gene segments are V lambda and J lambdagene segments.

Provision 33. The vertebrate or cell of provision 26, wherein endogenouslambda chain expression is substantially inactive.

Provision 34. The vertebrate or cell of provision 30, wherein theendogenous lambda chain expression is completely inactive.

Provision 35. The vertebrate or cell of provision 25, wherein thetargeted insert comprises inter-gene segment intervening sequences beinghuman lambda light chain locus DNA which is between functional human Vand J light chain gene segments in a human locus or comprises inter-genesegment intervening sequences being lambda light chain locus DNA whichis between corresponding lambda light chain gene segments in anendogenous genome.

Provision 36. The vertebrate or cell of provision 35, wherein thetargeted insert includes a pseudogene.

Provision 37. The vertebrate of provision 25, wherein the vertebrate isderived from a mouse ES cell or a rat ES cell.

Provision 38. The vertebrate of provision 25, wherein the vertebrate isa mouse or a rat.

Provision 38a. The vertebrate of provisions 25, wherein said human Vλand Jλ gene segments are positioned upstream to an endogenous lightchain constant region.

VJCλ into Kappa Locus

Provision 39. A non-human vertebrate or cell having a genome comprisinga recombinant immunoglobulin kappa light chain locus, said locuscomprising a targeted insert of human VA, Jλ and Cλ gene segmentspositioned upstream to an endogenous kappa constant region,

-   -   wherein said vertebrate or cell expresses immunoglobulin light        chains comprising human V-C regions derived from recombination        of human Vλ, Jλ, and Cλ gene segments, and    -   wherein said targeted insert comprises at least the functional        V, J and C gene segments from Vλ3-1 to Cλ7 of a human lambda        chain immunoglobulin locus.

Provision 40. The vertebrate or cell of provision 39, wherein saidtargeted insert comprises at least the functional V, J and C genesegments from Vλ2-18 to Cλ7 of a human lambda light chain immunoglobulinlocus.

Provision 41. The vertebrate or cell of provision 39, wherein thetargeted insert comprises inter-gene segment intervening sequences beinghuman lambda light chain locus DNA which is between functional human Vand J or J and C light chain gene segments in a human locus or comprisesinter-gene segment intervening sequences being lambda light chain locusDNA which is between corresponding lambda light chain gene segments inan endogenous non-human vertebrate genome.

Provision 42. The vertebrate or cell of provision 41, wherein thetargeted insert includes a pseudogene.

Provision 43. The vertebrate of provision 39, wherein the vertebrate isderived from a mouse ES cell or a rat ES cell.

Provision 44. The vertebrate of provision 39, wherein the vertebrate isa mouse or a rat.

Provision 45. The vertebrate or cell of provision 39, wherein theendogenous kappa chain expression is substantially inactive.

Provision 46. The vertebrate or cell of provision 45, wherein theendogenous kappa chain expression is completely inactive.

Provision 47. The vertebrate or cell of provision 39, wherein thetargeted insert is positioned downstream of endogenous V and J lightchain gene segments.

VJλ into Kappa Locus

Provision 48. A non-human vertebrate or cell having a genome comprisinga recombinant immunoglobulin kappa light chain locus, said locuscomprising endogenous Vκ and Jκ gene segments upstream to a targetedinsert,

-   -   wherein the targeted insert comprises at least the functional Vλ        and Jλ gene segments from Vλ3-1 to Cλ7 of a human lambda light        chain immunoglobulin locus,    -   wherein said vertebrate or cell expresses an immunoglobulin        light chain comprising a human lambda variable region, and    -   wherein expression of light chains comprising endogenous kappa        variable regions derived from recombination of endogenous Vκ and        Jκ gene segments is substantially inactive.

Provision 49. The vertebrate of provision 48, wherein the vertebrate isderived from a mouse ES cell or a rat ES cell.

Provision 50. The vertebrate of provision 48, wherein the vertebrate isa mouse or a rat.

Provision 51. The vertebrate or cell of provision 48, wherein saidtargeted insert comprises at least the functional Vλ and Jλ genesegments from Vλ2-18 to Cλ7 of a human lambda light chain immunoglobulinlocus.

Provision 52. The vertebrate or cell of provision 48, wherein endogenousVκ and Jκ light chain expression is completely inactive.

Provision 53. The vertebrate or cell of provision 48, wherein less than10, 5, 4, 3, 2, 1, or 0.5% of immunoglobulin light chains expressed bysaid vertebrate or cell comprise endogenous kappa variable regions.

Provision 54. The vertebrate or cell of provision 48, wherein thetargeted insert comprises inter-gene segment intervening sequences beinghuman lambda light chain locus DNA which is between functional human Vand J gene segments in a human locus or comprises inter-gene segmentintervening sequences being lambda light chain locus DNA which isbetween corresponding lambda light chain gene segments in an endogenousgenome.

Provision 55. A non-human vertebrate or cell, having a recombinantgenome comprising endogenous immunoglobulin kappa light chain locussequences comprising at least one endogenous kappa enhancer (Eκ)sequence, at least one endogenous V kappa gene segment, at least oneendogenous J kappa gene segment, and at least one endogenous C kappaconstant region,

-   -   wherein endogenous V kappa and J kappa gene segments are        separated from a respective endogenous Eκ sequence on the same        chromosome by a distance that substantially prevents production        of an endogenous immunoglobulin kappa light chain polypeptide.

Provision 56. The vertebrate or cell of provision 55, wherein theendogenous V kappa and J kappa gene segments are separated from therespective endogenous Eκ sequence by a distance that is greater than thedistance between endogenous V kappa and J kappa gene segments and arespective endogenous Eκ sequence in an endogenous, non recombinantkappa light chain locus.

Provision 57. The cell of provision 55, wherein the cell is a mouse cellor a rat cell.

Provision 57a. The vertebrate of provision 55, wherein the vertebrate isderived from a mouse ES cell or a rat ES cell.

Provision 58. The vertebrate of provision 55, wherein the vertebrate isa mouse or a rat.

Provision 59. The vertebrate or cell of provision 55, wherein saidrecombinant genome comprises a targeted insert comprising one or morehuman V light chain gene segments and one or more human J light chaingene segments,

-   -   wherein the targeted insert is positioned between said        endogenous V kappa and J kappa gene segments and said respective        endogenous Eκ sequence.

Provision 59a. The vertebrate or cell of provision 59, wherein saidrecombinant genome is homozygous for the targeted insert.

Provision 60. The vertebrate or cell of provision 59, wherein thetargeted insert comprises light chain gene segments comprising one ormore human Vκ and one or more Jκ gene segments.

Provision 60a. The vertebrate or cell of provision 60, wherein saidrecombinant genome is homozygous for the targeted insert.

Provision 61. The vertebrate or cell of any preceding provision, whereinthe targeted insert comprises a repertoire of human Vλ and Jλ genesegments and wherein the targeted insert has been inserted within 100 kbof an endogenous light chain locus enhancer sequence.

Provision 62. The vertebrate or cell of any preceding provision, whereinthe targeted insert comprises a repertoire of at least 10 human Vλ geneor human Jλ gene segments and wherein the targeted insert is positionedupstream to an endogenous light chain constant region.

Provision 63. The vertebrate or cell of provision 62, wherein thetargeted insert comprises at least a portion of a human immunoglobulinlambda chain locus from Vλ2-18 to Vλ3-1.

Provision 64. The vertebrate or cell of provision 62, wherein thetargeted insert comprises at least 2, 3, 4, or 5 human Jλ gene segments.

Provision 65. The vertebrate or cell of provision 64, wherein the humanJλ gene segments are different from each other.

Provision 66. The vertebrate or cell of provision 65, wherein the humanJλ gene segments are Jλ1, Jλ2, Jλ3, Jλ6, and Jλ7.

Provision 67. The vertebrate or cell of provision 62, wherein thetargeted insert includes at least a portion of a human immunoglobulinlambda chain locus from Vλ2-18 to Cλ7.

Provision 68. The vertebrate or cell of provision 62, wherein thetargeted insert excludes human Jλ4Cλ4 and/or human Jλ5Cλ5.

Provision 69. The vertebrate or cell of provision 62, wherein thetargeted insert includes a human light chain enhancer.

Provision 70. The vertebrate or cell of provision 69, wherein the humanlight chain enhancer is an Eλ sequence and wherein the Eλ sequence ispositioned between the human Jλ gene segments and an endogenous lightchain constant region.

Provision 71. The vertebrate or cell of provision 70, wherein the humanJλ gene segments are part of a human JλCλ cluster.

Provision 72. The vertebrate or cell of any preceding provision, whereinthe vertebrate or cell expresses lambda immunoglobulin light chainscomprising a repertoire of human lambda variable regions encoded byhuman Vλ and Jλ gene segments, wherein the human Vλ includes Vλ3-1 and,optionally, one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11,Vλ3-10, Vλ3-9, Vλ2-8, and Vλ4-3, wherein the human Vλ and Jλ genesegments are included in the targeted insert.

Provision 73. The vertebrate or cell of any preceding provision, whereinthe vertebrate or cell expresses lambda immunoglobulin light chainscomprising a repertoire of human lambda variable regions encoded byhuman Vλ and Jλ gene segments, wherein the human Vλ includes Vλ2-14 and,optionally, one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11,Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3, and Vλ3-1, wherein the human Vλ and Jλ genesegments are included in the targeted insert.

Provision 74. The vertebrate or cell of any preceding provision, whereinthe vertebrate or cell expresses lambda immunoglobulin light chainscomprising a repertoire of human lambda variable regions encoded byhuman Vλ and Jλ gene segments, wherein the human Vλ includes includingVλ2-8 and, optionally, one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12,Vλ2-11, Vλ3-10, Vλ3-9, Vλ4-3, and Vλ3-1, wherein the human Vλ and Jλgene segments are included in the targeted insert.

Provision 75. The vertebrate or cell of any preceding provision, whereinthe vertebrate or cell expresses lambda immunoglobulin light chainscomprising a repertoire of human lambda variable regions encoded byhuman Vλ and Jλ gene segments, wherein the human Vλ includes Vλ3-10 and,optionally, one or more of Vλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11,Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3, and Vλ3-1, wherein the human Vλ and Jλ genesegments are included in the targeted insert.

Provision 76. The vertebrate or cell of any preceding provision, whereinthe targeted insert comprises each functional Vλ gene segment fromVλ2-18 to Vλ3-1 of a human lambda light chain locus.

Provision 77. The vertebrate or cell of any preceding provision, whereinat least a human Vλ3-1 is included in the targeted insert.

Provision 78. The vertebrate or cell of provision 77, wherein at leastVλ2-18, Vλ3-16, V2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3, andVλ3-1 are included in the targeted insert.

Provision 79. The vertebrate of any preceding provision, wherein thevertebrate expresses more lambda chains than kappa chains.

Provision 80. The vertebrate of any preceding provision, wherein thevertebrate expresses no endogenous kappa chains.

Provision 81. The vertebrate of any preceding provision, whereinendogenous kappa chain expression is substantially inactive.

Provision 82. The vertebrate of provision 81, wherein the endogenouskappa chain expression is completely inactive.

Provision 83. The vertebrate of any preceding provision, wherein thevertebrate expresses immunoglobulin heavy chains.

Provision 84. The vertebrate or cell of any preceding provision, whereinthe targeted insert includes a human lambda enhancer (Eλ) sequence andwherein the Eλ sequence is positioned in said endogenous light chainlocus.

Provision 85. The vertebrate or cell of provision 84, wherein the Eλsequence is positioned downstream to a 3′-most downstream Cλ region thatis included in the targeted insert.

Provision 86. The vertebrate or cell of any preceding provision, whereinat least human JC gene segments Jλ1-Cλ1, Jλ2-Cλ2, Jλ3-Cλ3, Jλ6-Cλ6, andJλ7-Cλ7 are included in the targeted insert.

Provision 87. The vertebrate or cell of any preceding provision, whereinthe human gene segments included in the targeted insert are in germlineconfiguration.

Provision 88. The vertebrate or cell of provision 87, wherein thetargeted insertion comprises inter-gene segment sequences of a humanlight chain locus or inter-gene segment sequences of an endogenous lightchain locus.

Provision 89. The vertebrate or cell of any preceding provision, whereinan endogenous light chain enhancer remains in the endogenous locus.

Provision 90. The vertebrate or cell of provision 89, wherein theendogenous enhancer is in germline configuration.

Provision 91. The vertebrate or cell of provision 90, wherein theendogenous locus is a kappa locus.

Provision 92. The vertebrate or cell of provision 90, wherein theendogenous kappa enhancer is present.

Provision 93. The vertebrate or cell of provision 92, wherein theendogenous enhancer is an iEκ and/or 3′ Eκ sequence.

Provision 94. The vertebrate or cell of provision 90, wherein thegermline configuration is with respect to an endogenous light chainconstant region.

Provision 95. The vertebrate or cell of any preceding provision, whereinthe genome is heterozygous for the targeted insert.

Provision 96. The vertebrate or cell of provision 95, wherein thetargeted insert comprises human V and J or human V, J, and C light chaingene segments.

Provision 97. The vertebrate or cell of provision 96, wherein thetargeted insert is positioned in an endogenous light chain lambda locus.

Provision 98. The vertebrate or cell of provision 96, wherein thetargeted insert is positioned in an endogenous light chain kappa locus.

Provision 99. The vertebrate or cell of provision 98, wherein theendogenous kappa enhancer is present and is an iEκ and/or 3′ Eκsequence.

Provision 100. The vertebrate of provision 95, wherein the vertebrate isderived from a mouse ES cell or a rat ES cell.

Provision 101. The vertebrate of provision 95, wherein the vertebrate isa mouse or a rat.

Provision 102. The vertebrate or cell of provision 95, wherein thegenome comprises a first targeted insert comprising a human lambda genesegment and a second targeted insert comprising human kappaimmunoglobulin V and J gene segments,

-   -   wherein the first targeted insert is positioned in a first        endogenous kappa locus and wherein the second targeted insert is        positioned in a second endogenous kappa locus and upstream to an        endogenous kappa constant region.

Provision 103. The vertebrate or cell of provision 102, wherein anendogenous kappa light chain enhancer is present in the first and/orsecond endogenous kappa locus.

Provision 104. The vertebrate or cell of provision 103, wherein theendogenous kappa loci are optionally in germline configuration.

Provision 105. The vertebrate or cell of provision 95, wherein thegenome comprises a first targeted insert comprising a human lambda genesegment and a second targeted insert comprising human kappaimmunoglobulin V and J gene segments,

-   -   wherein the first targeted insert is positioned in a first        endogenous lambda locus and wherein the second targeted insert        is positioned in a second endogenous lambda locus and upstream        to an endogenous lambda constant region.

Provision 106. The vertebrate or cell of provision 105, wherein anendogenous lambda light chain enhancer is present in the first and/orsecond endogenous lambda locus.

Provision 106. The vertebrate or cell of provision 105, wherein theendogenous kappa loci are optionally in germline configuration.

Provision 107. The vertebrate or cell of any preceding provision,wherein the genome is homozygous for a targeted insert comprising ahuman lambda gene segment and positioned in the endogenousimmunoglobulin light chain locus.

Provision 108. The vertebrate or cell of any preceding provision,wherein the genome comprises two or more targeted inserts comprisinghuman lambda gene segments and positioned in the endogenous kappa and/orlambda locus.

Provision 109. The vertebrate or cell of provision 108, wherein thegenome is homozygous for a first targeted insert comprising a humanlambda gene segment and positioned in each endogenous lambda locus,wherein the vertebrate or cell expresses lambda light chains comprisinghuman lambda variable regions;

-   -   wherein a second targeted insert comprising a human lambda gene        segment is positioned in a first endogenous kappa locus,    -   wherein a third targeted insert comprising a plurality of human        Vκ and Jκ gene segments is positioned upstream to an endogenous        Cκ gene segment in a second endogenous kappa locus, and    -   wherein the vertebrate or cell expresses kappa light chains        comprising human kappa variable regions.

Provision 110. The vertebrate or cell of provision 108, wherein thetargeted inserts comprising a lambda gene segment is positioned in theendogenous kappa and lambda loci comprise the same repertoire of humanlambda gene segments.

Provision 111. The vertebrate or cell of provision 109, wherein thefirst and second targeted inserts comprise the same repertoire of humanlambda gene segments.

Provision 112. The vertebrate or cell of provision 108, wherein thetargeted inserts comprising a lambda gene segment is positioned in thekappa loci and the targeted inserts positioned in the lambda locicomprise a different repertoire of human lambda gene segments.

Provision 113. The vertebrate or cell of provision 109, wherein thefirst and second targeted inserts comprise a different repertoire ofhuman lambda gene segments.

Provision 114. A non-human vertebrate or cell having a genome comprisingone or more first and/or second targeted inserts positioned in at leastone endogenous immunoglobulin locus, wherein the one or more firstand/or second targeted inserts each comprise a repertoire of humanimmunoglobulin gene segments,

-   -   the genome comprising one of the following light chain loci        arrangements:    -   (a) an L positioned in a first endogenous kappa chain locus and        a K positioned in a second endogenous kappa chain locus;    -   (b) an L positioned in a first endogenous lambda chain locus and        a K positioned in a second endogenous lambda chain allele;    -   (c) an L positioned in each endogenous kappa chain loci;    -   (d) an L positioned in each endogenous lambda chain loci;    -   (e) an L positioned in a first endogenous kappa chain locus and        with a second endogenous kappa chain locus is inactive; or    -   (f) an L positioned in a first endogenous lambda chain locus and        with a second endogenous lambda chain locus is inactive;        wherein    -   an L represents a first targeted insert comprising at least        functional human Vλ and Jλ gene segments from Vλ3-1 to Cλ7        comprised by a human lambda chain immunoglobulin locus;        wherein    -   a K represents a second targeted insert comprising human Vκ and        Jκ gene segments; and    -   wherein each L or K is positioned upstream to a constant region,        thereby allowing expression of light chains comprising human V        regions derived from recombination of human V and J gene        segments.

Provision 115. The vertebrate of provision 114, wherein the vertebrateis derived from a mouse ES cell or a rat ES cell.

Provision 116. The vertebrate of provision 114, wherein the vertebrateis a mouse or a rat.

Provision 117. The vertebrate or cell of provision 114, wherein Lfurther comprises a human Cλ region

Provision 118. The vertebrate or cell of provision 114, wherein the Lcomprises functional human lambda chain immunoglobulin gene segmentsfrom Vλ2-18 to Cλ7.

Provision 119. The vertebrate or cell of provision 114, wherein thegenome comprises one of the following light chain loci arrangements:

-   -   (a) and an L positioned in the first or in the first and second        endogenous lambda chain loci;    -   (a) and a K positioned in the first or in the first and second        endogenous lambda chain loci;    -   (a) and an L positioned in the first endogenous lambda chain        locus and a K positioned in the second endogenous lambda chain        locus;    -   (b) and an L positioned in the first or in the first and second        endogenous kappa chain loci;    -   (b) and a K positioned in the first or in the first and second        endogenous kappa chain loci;    -   (b) and an L positioned in the first endogenous kappa chain        locus and a K positioned in the second endogenous kappa chain        locus;    -   (c) and a K positioned in the first or in the first and second        endogenous lambda chain loci;    -   (c) and an L positioned in the first or in the first and second        endogenous lambda chain loci;    -   (c) and an L positioned in the first endogenous lambda chain        locus and a K positioned in the second endogenous lambda chain        locus;    -   (c) and with the first and second endogenous lambda chain loci        is inactive; (d) and an L positioned in the first or in the        first and second endogenous kappa chain loci;    -   (d) and a K positioned in the first or in the first and second        endogenous kappa chain loci;    -   (d) and an L positioned in the first endogenous kappa chain        locus and a K positioned in the second endogenous kappa chain        locus; or    -   (d) and with the first and second endogenous kappa chain loci is        inactive.

Provision 120. The vertebrate or cell of provision 114, whereinendogenous kappa chain expression is substantially inactive.

Provision 121. The vertebrate or cell of provision 120, wherein theendogenous kappa chain expression is completely inactive.

Provision 122. The vertebrate or cell of provision 114, whereinendogenous lambda chain expression is substantially inactive.

Provision 123. The vertebrate or cell of provision 122, wherein theendogenous lambda chain expression is completely inactive.

Provision 124. The vertebrate or cell of provision 114, wherein one ormore L's are positioned upstream to an endogenous lambda or kappaconstant region.

Provision 125. The vertebrate or cell of provision 114, wherein one ormore L's positioned in a lambda locus is positioned upstream to anendogenous lambda constant region.

Provision 126. The vertebrate or cell of provision 114, wherein one ormore L's positioned in a kappa locus is positioned upstream to anendogenous kappa constant region.

Provision 127. The vertebrate or cell of provision 114, wherein each Lpositioned in a lambda locus is positioned upstream to a human lambdaconstant region.

Provision 128. The vertebrate or cell of provision 114, wherein each Lpositioned in a kappa locus is positioned upstream to a human kappaconstant region.

Provision 129. The vertebrate or cell of provision 114, wherein one ormore K's are positioned upstream to an endogenous lambda or kappaconstant region.

Provision 130. The vertebrate or cell of provision 114, wherein one ormore K's positioned in a lambda locus is positioned upstream to anendogenous lambda constant region.

Provision 131. The vertebrate or cell of provision 114, wherein each Kpositioned in a kappa locus is positioned upstream to an endogenouskappa constant region.

Provision 132. The vertebrate or cell of provision 114, wherein each Kpositioned in a lambda locus is positioned upstream to a human lambdaconstant region.

Provision 133. The vertebrate or cell of provision 114, wherein each Kpositioned in a kappa locus is positioned upstream to a human kappaconstant region.

Provision 134. The vertebrate or cell of provision 114, wherein thegenome comprises more than one L and each L comprises a differentrepertoire of human Vλ and Jλ gene segments.

Provision 135. The vertebrate or cell of provision 134, wherein thegenome comprises two L's.

Provision 136. The vertebrate or cell of provision 134, wherein thegenome comprises three L's.

Provision 137. The vertebrate or cell of provision 114, wherein thegenome comprises more than one L and each L comprises a differentrepertoire of human Vλ, Jλ, and Cλ gene segments.

Provision 138. The vertebrate or cell of provision 114, wherein thegenome comprises more than one K and each K comprises a differentrepertoire of human Vκ and Jκ gene segments.

Provision 139. The vertebrate or cell of provision 138, wherein thegenome comprises two L's.

Provision 140. The vertebrate or cell of provision 138, wherein thegenome comprises three K's.

Provision 141. The vertebrate or cell of provision 114, wherein thegenome comprises more than one L and each L comprises a differentrepertoire of human Vκ, Jκ, and Cκ gene segments.

Provision 141a. The vertebrate of provision 114, wherein the vertebrateis derived from a mouse ES cell or a rat ES cell.

Provision 142. The vertebrate or cell of any preceding provision,wherein the genome comprises an immunoglobulin heavy chain locuscomprising human VH gene segments.

Provision 143. A method for producing an antibody or light chaincomprising a lambda variable region specific to a desired antigen, themethod comprising immunizing a vertebrate according to any precedingprovision with the desired antigen and recovering the antibody or lightchain or recovering a cell producing the antibody or light chain.

Provision 144. The method of provision 143, further comprising a step ofreplacing the non-human vertebrate constant region with a human constantregion thereby producing a humanised antibody or antibody light chain.

Provision 145. The method of provision 144, wherein the humanisedantibody or antibody light chain is produced by engineering a nucleicacid encoding the fully humanised antibody or light chain.

Provision 146. A humanised antibody or antibody light chain produced bythe method of provision 143.

Provision 147. A derivative of the humanised antibody or antibody lightchain of provision 146.

Provision 148. A pharmaceutically composition comprising the humanisedantibody or antibody light chain produced by the method of provision 143a pharmaceutically acceptable carrier, excipient, or diluent.

Provision 149. A method for inactivating endogenous IgK-VJ gene segmentsin a genome of a non-human vertebrate or cell, the method comprisespositioning in the genome a targeted insert comprising humanimmunoglobulin gene segments, wherein the targeted insert is positionedbetween an endogenous IgK-VJ gene segment and Eκ enhancer sequence whichincreases the physical distance between the endogenous IgK-VJ and the Eκenhancer, thereby inactivating the endogenous IgK-VJ gene segments.

Provision 150. The method of provision 149, wherein the non-humanvertebrate is a mouse or rat.

Provision 150a. The method of provision 148, wherein the vertebratedeveloped from a mouse ES cell or a rat ES cell.

Provision 151. The method of provision 149, wherein the cell is a mousecell or a rat cell.

Provision 152. The method of provision 149, wherein the humanimmunoglobulin gene segments comprise human VL and JL gene segments.

Provision 153. The method of provision 152, wherein human VL and JL genesegments comprise human Vλ and Jλ gene segments and/or human Vκ and Jκgene segments.

Provision 154. A method for obtaining a pool of immunoglobulin lightchains wherein at least 80% of the immunoglobulin light chains comprisehuman Vλ and Jλ regions, the method comprising

-   -   providing the vertebrate or cell of provision 1 and    -   isolating a sample comprising the immunoglobulin light chains.

Provision 154a. The method of provision 154, further comprising a stepof isolating the immunoglobulin light chains from the sample.

Provision 154b. The method of provision 154a, wherein the sample isserum, spleen, thymus, lymph node, or appendix.

Provision 154c. The method of provision 154b wherein the spleencomprises splenic tissue containing B-cells.

Provision 154d. The method of provision 154c, further comprising a stepof isolating B-cells from splenic tissue.

Provision 155. The method of provision 154, wherein the immunoglobulinlight chains are included in antibodies or antibody fragments.

Provision 156. An antibody or antibody fragment isolated in the methodof provision 155.

Provision 156a. A derivative of the antibody or antibody fragment ofprovision 156.

Provision 157. A pharmaceutical composition comprising the antibody orantibody fragment of provision 156 and a pharmaceutically acceptablecarrier, excipient, or diluent.

Provision 158. The method of provision 154, comprising a step ofimmunizing the vertebrate with an antigen before the step of isolating asample comprising the immunoglobulin light chains.

Provision 159. A method for obtaining a pool of immunoglobulin lightchains wherein at least 60% of the immunoglobulin light chains comprisehuman lambda light chains, the method comprising

-   -   providing the vertebrate or cell of provision 19 and    -   isolating a sample comprising the immunoglobulin light chains.

Provision 159a. The method of provision 159, further comprising a stepof isolating the immunoglobulin light chains from the sample.

Provision 159b. The method of provision 159a, wherein the sample isserum, spleen, thymus, lymph node, or appendix.

Provision 159c. The method of provision 159b wherein the spleencomprises splenic tissue containing B-cells.

Provision 159d. The method of provision 159c, further comprising a stepof isolating B-cells from splenic tissue.

Provision 160. The method of provision 159, wherein the immunoglobulinlight chains are included in antibodies or antibody fragments.

Provision 161. An antibody or antibody fragment isolated in the methodof provision 160.

Provision 161a. A derivative of the antibody or antibody fragment ofprovision 161.

Provision 162. A pharmaceutical composition comprising the antibody orantibody fragment of provision 161 and a pharmaceutically acceptablecarrier, excipient, or diluent.

Provision 163. The method of provision 159, comprising a step ofimmunizing the vertebrate with an antigen before the step of isolating asample comprising the immunoglobulin light chains.

Provision 164. A method for expressing human immunoglobulin VJC lightchains in a non-human vertebrate, the method comprising

-   -   providing the vertebrate or cell of provision 40 and    -   isolating a sample comprising the immunoglobulin VJC light        chains.

Provision 164a. The method of provision 164, wherein the non-humanvertebrate develops from an ES cell.

Provision 164a. The method of provision 164, further comprising a stepof isolating the immunoglobulin light chains from the sample.

Provision 164b. The method of provision 164a, wherein the sample isserum, spleen, thymus, lymph node, or appendix.

Provision 164c. The method of provision 164b wherein the spleencomprises splenic tissue containing B-cells.

Provision 164d. The method of provision 164c, further comprising a stepof isolating B-cells from splenic tissue.

Provision 165. The method of provision 164, wherein the immunoglobulinVJC light chains are included in antibodies or antibody fragments.

Provision 166. An antibody or antibody fragment isolated in the methodof provision 165.

Provision 166a. A derivative of the antibody or antibody fragment ofprovision 166.

Provision 167. A pharmaceutical composition comprising the antibody orantibody fragment of provision 166 and a pharmaceutically acceptablecarrier, excipient, or diluent.

Provision 168. The method of provision 164, comprising a step ofimmunizing the vertebrate with an antigen before the step of isolating asample comprising the immunoglobulin VJC light chains.

Provision 169. The method of provision 164, wherein the vertebratedeveloped from a mouse ES cell or a rat ES cell.

Provision 39N. A non-human vertebrate having a genome comprising arecombinant immunoglobulin light chain locus, said locus comprising atargeted insert positioned in an endogenous light chain locus,

-   -   wherein the targeted insert comprises human lambda light chain        locus DNA and is positioned upstream to a lambda light chain        constant region,    -   wherein said targeted insert includes a repertoire of human Vλ        and Jλ gene segments,    -   wherein the vertebrate expresses immunoglobulin light chains        comprising human lambda variable regions, and    -   wherein at least 80% of the immunoglobulin light chains that        comprise lambda variable regions expressed in said vertebrate        comprises human lambda variable regions.

Provision 40N. A non-human vertebrate having a genome comprising arecombinant immunoglobulin light chain locus, said locus comprising atargeted insert positioned in an endogenous light chain locus,

-   -   wherein the targeted insert comprises human lambda light chain        locus DNA which is positioned upstream to a lambda light chain        constant region and includes a repertoire of human Vλ and Jλ        gene segments,    -   wherein said genome comprises kappa V gene segments positioned        upstream to a light chain constant region,    -   wherein the vertebrate expresses immunoglobulin light chains        comprising lambda variable regions, and    -   wherein at least 60% of immunoglobulin light chains expressed by        said vertebrate comprises human lambda variable regions.

Provision 47N. A method for obtaining a pool of immunoglobulin lightchains wherein at least 80% of the immunoglobulin light chains comprisehuman Vλ and Jλ regions, the method comprising

-   -   providing the vertebrate or cell of provision 39N and    -   isolating a sample comprising the immunoglobulin light chains.

Provision 48N. A method for obtaining a pool of immunoglobulin lightchains wherein at least 60% of the immunoglobulin light chains comprisehuman lambda light chains, the method comprising

-   -   providing the vertebrate or cell of provision 40N and    -   isolating a sample comprising the immunoglobulin light chains.

Provision 49N. A method for obtaining an immunoglobulin light chaincomprising a human lambda variable region from a pool of immunoglobulinlight chains, the method comprising

-   -   providing the vertebrate or cell of provision 40N, thereby        providing pool of immunoglobulin light chains wherein at least        60% of the immunoglobulin light chains comprise human lambda        variable regions and    -   isolating one or more immunoglobulin light chains from the pool,        wherein each isolated immunoglobulin light chain comprises a        human lambda variable region.

Provision 50N. A method for obtaining an immunoglobulin light chaincomprising a human lambda variable region from a pool of immunoglobulinlight chains, the method comprising

-   -   selecting a mouse that expresses immunoglobulin lambda light        chains containing human variable regions,    -   wherein the mouse comprises a targeted insert positioned        upstream to a light chain constant region,    -   wherein the targeted insert comprises human immunoglobulin Vλ        and Jλ gene segments,    -   wherein at least 80% of the immunoglobulin light chains that        comprise lambda variable regions expressed in said vertebrate        comprises human lambda variable regions,    -   wherein endogenous kappa and lambda chain expression is        substantially inactive, collecting serum from said mouse; and    -   isolating one or more immunoglobulin light chains from the        collected serum, wherein each isolated immunoglobulin light        chain comprises a human lambda variable region.

Provision 51N. A method for obtaining an immunoglobulin light chaincomprising a human lambda variable region from a pool of immunoglobulinlight chains, the method comprising

-   -   selecting a mouse that expresses immunoglobulin lambda light        chains containing human variable regions,    -   wherein the mouse comprises a targeted insert positioned        upstream to a light chain constant region,    -   wherein the targeted insert comprises human immunoglobulin Vλ        and Jλ gene segments,    -   wherein at least 60% of immunoglobulin light chains expressed by        said vertebrate comprises human lambda variable regions,    -   wherein endogenous kappa and lambda chain expression is        substantially inactive, collecting serum from said mouse; and    -   isolating one or more immunoglobulin light chains from the        collected serum, wherein each isolated immunoglobulin light        chain comprises a human lambda variable region.

Provision 52N. A method for obtaining an immunoglobulin light chaincomprising a human lambda variable region from a pool of immunoglobulinlight chains, the method comprising

-   -   selecting a mouse that expresses immunoglobulin lambda light        chains containing human variable regions,    -   wherein the mouse comprises a targeted insert positioned        upstream to a light chain constant region,    -   wherein the targeted insert comprises human immunoglobulin Vλ        and Jλ gene segments,    -   wherein at least 80% of the immunoglobulin light chains that        comprise lambda variable regions expressed in said vertebrate        comprises human lambda variable regions,    -   wherein at least 60% of immunoglobulin light chains expressed by        said vertebrate comprises human lambda variable regions,    -   wherein endogenous kappa and lambda chain expression is        substantially inactive, collecting serum from said mouse; and    -   isolating one or more immunoglobulin light chains from the        collected serum, wherein each isolated immunoglobulin light        chain comprises a human lambda variable region.

The following definitions apply to any configuration, aspect, provision,clause, attribute, example or embodiment of the invention.

“Derived from” is used in the ordinary sense of the term. Exemplarysynonyms include “produced as”, “resulting from”, “received from”,“obtained from”, “a product of”, “consequence of”, and “modified from”For example, a human variable region of a heavy chain can be derivedfrom recombination of human VH, D and JH gene segments and this reflectsthe in vivo recombination of these gene segments in, for example, atransgenic heavy chain locus according to the invention with anyaccompanying mutation (eg, junctional mutation).

Samples from which B-cells can be obtained include but are not limitedto blood, serum, spleen, splenic tissue, bone marrow, lymph, lymph node,thymus, and appendix. Antibodies and immunoglobulin chains can beobtained form each of the previous-mentioned samples and also from thefollowing non-limiting list of B-cells, ascites fluid, hybridomas, andcell cultures.

“Plurality” is used in the ordinary sense of the term and means “atleast one” or “more than one”.

The term “germline configuration” refers to a germline genomicconfiguration. For example, human immunoglobulin gene segments of atransgenic immunoglobulin locus are in a germline configuration when therelative order of the gene segments is the same as the order ofcorresponding gene segments in a human germline genome. For example,when the transgenic locus is a heavy chain locus of the inventioncomprising hypothetical human immunoglobulin gene segments A, B and C,these would be provided in this order (5′ to 3′ in the locus) when thecorresponding gene segments of a human germline genome comprises thearrangement 5′-A-B-C-3′. In an example, when elements of a humanimmunoglobulin locus (eg, gene segments, enhancers or other regulatoryelements) are provided in a transgenic immunoglobulin locus according tothe invention, the human Ig locus elements are in germline configurationwhen the relative order of the gene segments is the same as the order ofcorresponding gene segments in a human germline genome and humansequences between the elements are included, these corresponding to suchsequences between corresponding elements in the human germline genome.Thus, in a hypothetical example the transgenic locus comprises humanelements in the arrangement 5′-A-S1-B-S2-C-S3-3′, wherein A, B and C arehuman immunoglobulin gene segments and S1-S3 are human inter-genesegment sequences, wherein the corresponding arrangement5′-A-S1-B-S2-C-S3-3′ is present in a human germline genome. For example,this can be achieved by providing in a transgenic immunoglobulin locusof the invention a DNA insert corresponding to the DNA sequence from Ato C in a human germline genome (or the insert comprising the DNAsequence from A to C). The arrangements in human germline genomes andimmunoglobulin loci are known in the art (eg, see the IMGT at the WorldWide Web (see above), Kabat and other antibody resources referencedherein).

The term “antibody” includes monoclonal antibodies (including fulllength antibodies which have an immunoglobulin Fc region), antibodycompositions with polyepitopic specificity, multispecific antibodies(e.g., bispecific antibodies, diabodies, and single-chain molecules, aswell as antibody fragments (e.g., dAb, Fab, F(ab′)2, and Fv). The term“antibody” also includes H2 antibodies that comprise a dimer of a heavychain (5′-VH-(optional Hinge)-CH2-CH3-3′) and are devoid of a lightchain (akin to naturally-occurring H2 antibodies; see, eg, Nature. 1993Jun. 3; 363(6428):446-8; Naturally occurring antibodies devoid of lightchains; Hamers-Casterman C, Atarhouch T, Muyldermans S, Robinson G,Hamers C, Songa E B, Bendahman N, Hamers R). Thus, in an embodiment ofthe present invention, RNA produced from the transgenic heavy chainlocus encodes for heavy chains that re devoid of a CH1 gene segment andcomprise no functional antibody light chain. In an example, RNA producedfrom the transgenic heavy chain locus encodes for VH single variabledomains (dAbs; domain antibodies). These can optionally comprise aconstant region.

The term “immunoglobulin” (Ig) is used interchangeably with “antibody”herein.

An “isolated” antibody is one that has been identified, separated and/orrecovered from a component of its production environment (e.g.,naturally or recombinantly). Preferably, the isolated polypeptide isfree of association with all other components from its productionenvironment, eg, so that the antibody has been isolated to anFDA-approvable or approved standard. Contaminant components of itsproduction environment, such as that resulting from recombinanttransfected cells, are materials that would typically interfere withresearch, diagnostic or therapeutic uses for the antibody, and mayinclude enzymes, hormones, and other proteinaceous or non-proteinaceoussolutes. In preferred embodiments, the polypeptide will be purified: (1)to greater than 95% by weight of antibody as determined by, for example,the Lowry method, and in some embodiments, to greater than 99% byweight; (2) to a degree sufficient to obtain at least 15 residues ofN-terminal or internal amino acid sequence by use of a spinning cupsequenator, or (3) to homogeneity by SDS-PAGE under non-reducing orreducing conditions using Coomassie blue or, preferably, silver stain.Isolated antibody includes the antibody in situ within recombinant cellssince at least one component of the antibody's natural environment willnot be present. Ordinarily, however, an isolated polypeptide or antibodywill be prepared by at least one purification step.

An “antibody fragment” comprises a portion of an intact antibody,preferably the antigen binding and/or the variable region of the intactantibody. Examples of antibody fragments include dAb, Fab, Fab′, F(ab′)2and Fv fragments; diabodies; linear antibodies; single-chain antibodymolecules and multispecific antibodies formed from antibody fragments.

An antibody that “specifically binds to” or is “specific for” aparticular polypeptide, antigen, or epitope is one that binds to thatparticular polypeptide, antigen, or epitope without substantiallybinding to other polypeptides, antigens or epitopes. For example,binding to the antigen or epitope is specific when the antibody bindswith a K_(D) of 100 μM or less, 10 μM or less, 1 μM or less, 100 nM orless, eg, 10 nM or less, 1 nM or less, 500 μM or less, 100 μM or less,or 10 μM or less. The binding affinity (K_(D)) can be determined usingstandard procedures as will be known by the skilled person, eg, bindingin ELISA and/or affinity determination using surface plasmon resonance(eg, Biacore™ or KinExA™ solution phase affinity measurement which candetect down to fM affinities (Sapidyne Instruments, Idaho)).“Pharmaceutically acceptable” refers to approved or approvable by aregulatory agency of the USA Federal or a state government or listed inthe U.S. Pharmacopeia or other generally recognized pharmacopeia for usein animals, including humans. A “pharmaceutically acceptable carrier,excipient, or adjuvant” refers to an carrier, excipient, or adjuvantthat can be administered to a subject, together with an agent, e.g., anyantibody or antibody chain described herein, and which does not destroythe pharmacological activity thereof and is nontoxic when administeredin doses sufficient to deliver a therapeutic amount of the agent.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1-8 show an iterative process for insertion of a series of humanBACs into a mouse Ig locus

FIG. 3 illustrates targeting of the large insert vector 1 to the mouseES cell genome. Large insert: Vector 1-engineer the human BAC and targetit to the IgH locus. Genotyping: By linearizing the vector at the sameposition as the insertion of the stuffer sequence it is possible to usea gap-repair genotyping strategy which is short range (1 kb) and highlyspecific PCR, which could be universal. Validation: 1. CGH (ComparativeGenomic Hybridization) tiling array across the BAC sequence. 2. PCRValidation of all critical V, D & J regions.

FIGS. 9-18 show in more detail the process of FIGS. 1-8 for the IgH andkappa locus

FIGS. 19 and 20 show the principles behind antibody generation inchimaeric mice

FIG. 21 shows a possible insertion site for the human DNA in a mousechromosome

FIGS. 22-26 disclose an alternative iterative process for insertion of aseries of human BACs into a mouse Ig locus

FIGS. 27-29 illustrate a mechanism for inversion of the host VDJ region

FIG. 30 illustrates proof of principle for insertion of a plasmid usingan RMCE approach

FIG. 31 illustrates sequential RMCE—Integration into Landing Pad

FIG. 32 illustrates confirmation of Successful Insertion into LandingPad

FIG. 33 illustrates PCR Confirmation of 3′ End Curing

FIG. 34 illustrates insertion of BAC #1 and PCR Diagnostics

FIG. 35 illustrates JH and JK usage

FIG. 36 illustrates DH usage

FIG. 37 illustrates the distribution of CDR-H3 length in human VDJCμtranscripts from chimera mice

FIG. 38 illustrates the distribution of nucleotide numbers of deletionand insertion in IGH-VDI or IGK-VJ junctions

FIG. 39 illustrates Distribution of JH Usage Within Each VHs

FIGS. 40A and 40B illustrate Distribution of DH Usage Within Each VHs

FIG. 41A illustrates Nucleotide Gain or Loss at VJ Joints Generates IGKVariants; lines 1, 2-3, 4-7, 8-11, 12-17, 18-19 correspond to SEQ IDNOS: 69, 70, 71, 72, 73, 74, respectively.

FIG. 41B illustrates amino acid sequences of IGK Variants, lines 2-5(E6, F5, G6), 7-10 (E2), 12-15 (E10, G8), 17-20 (F3, F12), 22-25 (H1)correspond to SEQ ID NOS: 75-79, respectively.

FIG. 42A illustrates Hypermutaion in J Regions Generates IGK Variants;lines 1, 2-11, 12-15, 16-19 correspond to SEQ ID NOS: 80-83,respectively.

FIG. 42B illustrates IGK Variants, lines 2-4, 7-9, 12-14 correspond toSEQ ID NOS: 84-86, respectively.

FIG. 43 illustrates Joint Diversity Produces Functional CDS; lines 2-4(V1-5_J1_Ck), lines 6-8 (H12), lines 10-12 (V1-5_J4_Ck), lines 14-16(E1), lines 18-20 (E2), lines 22-24 (E8) correspond to SEQ ID NOS:87-92, respectively.

FIG. 44 illustrates a plot of identity of J_(H) gene segment use a5′-RACE Cμ-specific library generated from the splenic B lymphocytes oftransgenic mice according to the invention in which endogenous genesegment use has been inactivated by inversion

FIG. 45 illustrates the ratio of mouse V_(H) to human V_(H) usage asdetermined from antibody sequences from splenic B lymphocytes oftransgenic mice according to the invention in which endogenous genesegment use has been inactivated by inversion

FIG. 46 illustrates inversion strategy schematic

FIG. 47 illustrates targeting construct R57 for inversion

FIG. 48 illustrates sequence analysis from a Cμ-specific 5′-RACE libraryof splenic B lymphocytes of S1^(Inv1) (one human IGH BAC (ie, multiplehuman VH, all functional human D and JH) with an inverted endogenous IGHlocus) mouse shows that practically all the transcripts came fromrearranged human V_(H)-D-J_(H) gene segments

FIG. 49 illustrates that the S1^(Inv1) mouse shows a similar usage ofboth D and J_(H) gene segments to human

FIG. 50 illustrates that mouse V_(H) usage is further significantlyreduced following insertion of the 2^(nd) human BAC into the endogenousheavy chain locus

FIG. 51 illustrates a gel showing that normal class-switching (toIgG-type) was observed in transcripts from mice of the invention. Therearranged transcripts were detected using RT-PCR with human VH-specificand mouse Cγ-specific primers for amplification from peripheral bloodcells of immunized transgenic mice

FIG. 52 illustrates sequence analysis amplified fragments demonstratehypermutation occurred within the human variable regions of these IGγchains from mice of the invention; lines 1-12 correspond to SEQ ID NOS:93-104, respectively.

FIG. 53 illustrates Flow cytometric analysis showing normal B-cellcompartments in transgenic mice of the invention

FIGS. 54A-54D illustrate normal IgH isotypes in transgenic mice (H1)immunised with 100 μg Cholera Toxin B subunit. FIGS. 54E-54H illustratenormal IgH isotypes in transgenic mice (S1) immunised with 100 μgCholera Toxin B subunit.

FIGS. 55A and 55B illustrate normal IgH isotypes and serum levels areobtained in transgenic H1 and S1 animals, respectively, of the inventionfollowing immunisation with antigens.

FIG. 56, part 1 illustrates the first and second BACs used for insertioninto mouse endogenous light chain loci. The human DNA in each BAC isshown. Part 2 of FIG. 56 shows the insertion point of human lambda Iglocus DNA into the mouse endogenous kappa chain locus. Part 3 of FIG. 56shows the insertion point of human lambda Ig locus DNA into the mouseendogenous lambda chain locus.

FIG. 57 shows the results of FACS analysis to determine mouse and humanCλ expression (and thus correspondingly mouse and human variable regionexpression) in B220⁺ splenic B cells from P1 homozygous mice (P1/P1)compared to wild-type mice (WT).

FIG. 58A shows the results of FACS analysis to determine mouse Cκ and Cλexpression in B220⁺ splenic B cells from P2 homozygous mice (P2/P2)compared to wild-type mice (WT). No detectable mouse Cκ expression wasseen.

FIG. 58B shows the results of FACS analysis to determine human Cλexpression (and thus correspondingly human variable region expression)in B220⁺ splenic B cells from P2 homozygous mice (P2/P2) compared towild-type mice (WT).

FIG. 59 shows human Vλ usage in P2 homozygous mice (P2/P2) and typicalVλ usage in humans (inset)

FIG. 60 shows human Jλ usage in P2 homozygous mice (P2/P2) and typicalJλ usage in humans (inset)

FIG. 61 shows Vλ usage is very high in P2 homozygous mice (P2/P2).

FIG. 62 shows the distribution of mouse Vκ and human Vλ gene segmentusage from the chimaeric kappa locus in P2 homozygous mice (P2/P2).

FIG. 63 illustrates RSS arrangement in the lambda and kappa loci.

FIG. 64A shows the results of FACS analysis to determine mouse and humanCλ expression (and thus correspondingly mouse and human variable regionexpression) in B220⁺ splenic B cells from L2 homozygous mice in whichendogenous kappa chain expression has been inactivated (L2/L2; KA/KA)compared to mice having no human lambda DNA inserted and in whichendogenous kappa chain expression has been inactivated (KA/KA). Veryhigh human Vλ usage was seen in the L2/L2; KA/KA) mice, almost to theexclusion of mouse Vλ use.

FIG. 64B: Splenic B-Cell Compartment Analysis. This figure shows theresults of FACS analysis on splenic B-cells from transgenic L2/L2; KA/KAmice (L2 homozygotes; homozygous for human lambda gene segment insertioninto endogenous lambda loci; endogenous kappa chain expression havingbeen inactivated) compared with splenic B-cells from mice expressingonly mouse antibodies (KA/KA mice). The results show that the splenicB-cell compartments in the mice of the invention are normal (ie,equivalent to the compartments of mice expressing only mouse antibodychains).

FIG. 65: B-cell development and markers in the bone marrow and spleniccompartments.

FIG. 66A: Splenic B-Cell Compartment Analysis. This figure shows theresults of FACS analysis on splenic B-cells from transgenic S1F/HA, KA/+mice of the invention expressing heavy chain variable regions which areall human (where endogenous heavy chain expression has been inactivatedby inversion), compared with splenic B-cells from mice expressing onlymouse antibodies. The results show that the splenic B-cell compartmentsin the mice of the invention are normal (ie, equivalent to thecompartments of mice expressing only mouse antibody chains).

-   -   S1F/HA, +/KA=(i) S1F—first endogenous heavy chain allele has one        human heavy chain locus DNA insertion, endogenous mouse VDJ        region has been inactivated by inversion and movement upstream        on the chromosome; (ii) HA—second endogenous heavy chain allele        has been inactivated (by insertion of an endogenous interrupting        sequence); (iii)+—first endogenous kappa allele is a wild-type        kappa allele; and (iv) KA—the second endogenous kappa allele has        been inactivated (by insertion of an endogenous interrupting        sequence). This arrangement encodes exclusively for heavy chains        from the first endogenous heavy chain allele.

FIG. 66B: Splenic B-Cell Compartment Analysis. This figure shows theresults of FACS analysis on splenic B-cells from transgenic S1F/HA,K2/KA mice of the invention expressing heavy chain variable regionswhich are all human (where endogenous heavy chain expression has beeninactivated by inversion) and human kappa chain variable regions,compared with splenic B-cells from +/HA, K2/KA mice. The results showthat the splenic B-cell compartments in the mice of the invention arenormal.

-   -   S1F/HA, K2/KA=(i) K2—the first endogenous kappa allele has two        kappa chain locus DNA insertions between the most 3′ endogenous        Jκ and the mouse Cκ, providing an insertion of 14 human Vκ and        Jκ1-Jκ5; and (ii) KA—the second endogenous kappa allele has been        inactivated (by insertion of an endogenous interrupting        sequence). This arrangement encodes exclusively for heavy chains        comprising human variable regions and substantially kappa light        chains from the first endogenous kappa allele.    -   +/HA, K2/KA—this arrangement encodes for mouse heavy chains and        human kappa chains.

FIG. 67A-B: Bone marrow B progenitor compartment analysis. This figureshows the results of FACS analysis on bone marrow (BM) B-cells fromtransgenic S1F/HA, KA/+ mice of the invention expressing heavy chainvariable regions which are all human (where endogenous heavy chainexpression has been inactivated by inversion), compared with BM B-cellsfrom mice expressing only mouse antibodies. The results show that the BMB-cell compartments in the mice of the invention are normal (ie,equivalent to the compartments of mice expressing only mouse antibodychains).

FIG. 67C-D: Bone marrow B progenitor compartment analysis. This figureshows the results of FACS analysis on bone marrow (BM) B-cells fromtransgenic S1F/HA, K2/KA mice of the invention expressing heavy chainvariable regions which are all human (where endogenous heavy chainexpression has been inactivated by inversion) and human kappa chainvariable regions, compared with BM B-cells from +/HA, K2/KA mice. Theresults show that the BM B-cell compartments in the mice of theinvention are normal.

FIG. 68: shows Ig quantification for subtype and total Ig in variousmice: S1F/HA, KA/+=(i) S1F—first endogenous heavy chain allele has onehuman heavy chain locus DNA insertion, endogenous mouse VDJ region hasbeen inactivated by inversion and movement upstream on the chromosome;(ii) HA—second endogenous heavy chain allele has been inactivated (byinsertion of an endogenous interrupting sequence); (iii) KA—the firstendogenous kappa allele has been inactivated (by insertion of anendogenous interrupting sequence); and (iv)+—second endogenous kappaallele is a wild-type kappa allele. This arrangement encodes exclusivelyfor heavy chains from the first endogenous heavy chain allele.

-   -   S1F/HA, K2/KA=(i) K2—the first endogenous kappa allele has two        kappa chain locus DNA insertions between the most 3′ endogenous        Jκ and the mouse Cκ, providing an insertion of 14 human Vκ and        Jκ1-Jκ5; and (ii) KA—the second endogenous kappa allele has been        inactivated (by insertion of an endogenous interrupting        sequence). This arrangement encodes exclusively for heavy chains        comprising human variable regions and substantially kappa light        chains from the first endogenous kappa allele.    -   +/HA, K2/+—this arrangement encodes for mouse heavy chains and        both mouse and human kappa chains.    -   +/HA, +/KA—this arrangement encodes for mouse heavy and kappa        chains.

In this figure, “Sum Ig” is the sum of IgG and IgM isotypes.

FIG. 69: shows Ig quantification for subtype and total Ig in variousmice: S1F/HA, K2/KA (n=15) and 12 mice expressing only mouse antibodychains (+/HA, +/KA (n=6) and wild-type mice (WT; n=6)).

SEQUENCES

SEQ ID No 1 is a Rat switch sequence

SEQ ID No 2 is a landing pad targeting vector (long version)

SEQ ID No 3 is a landing pad targeting vector (shorter version)

SEQ ID No 4 is the mouse strain 129 switch

SEQ ID No 5 is the mouse strain C57 switch

SEQ ID No 6 is the 5′ homology arm of a landing pad

SEQ ID No 7 is oligo HV2-5

SEQ ID No 8 is oligo HV4-4

SEQ ID No 9 is oligo HV1-3

SEQ ID No 10 is oligo HV1-2

SEQ ID No 11 is oligo HV6-1

SEQ ID No 12 is oligo Cμ

SEQ ID No 13 is oligo KV1-9

SEQ ID No 14 is oligo KV1-8

SEQ ID No 15 is oligo KV1-6

SEQ ID No 16 is oligo KV1-5

SEQ ID No 17 is oligo Cκ

SEQ ID Nos 18-20 are rat switch sequences

SEQ ID No 21 is X₁X₂ T F G Q, where X₁X₂=PR, RT, or PW

SEQ ID No 22 is X₁X₂ T F G Q G T K V E I K R A D A, where X₁X₂=PR, RT,or PW;

SEQ ID No 23 is X₃X₄ T F G Q, where X₃X₄=PR or PW

SEQ ID No 24 is X₃X₄ T F G Q G T K V E I K R A D A, where X₃X₄=PR or PW

SEQ ID No 25 is Primer E1554

SEQ ID No 26 is Primer E1555

SEQ ID No 27 is Primer ELP1352_Cy1

SEQ ID No 28 is Primer ELP1353_Cy2b

SEQ ID No 29 is Primer ELP1354_Cy2a

SEQ ID No 30 is Primer ELP1356_VH4-4

SEQ ID No 31 is Primer ELP1357_VH1-2,3

SEQ ID No 32 is Primer ELP1358_VH6-1

SEQ ID No 33 is Primer mIgG1_2 rev

SEQ ID No 34 is Primer mIgG2b rev

SEQ ID No 35 is Primer mIgG2a_2 rev

SEQ ID No 36 is Primer mCH1 unirev

SEQ ID No 37 is Primer mCH1 unirev_2

SEQ ID Nos 38-45 are CDRH3 sequences

SEQ ID Nos 46-50 is 3, 4, 5, 6 or more (up to 82) repeats of GGGCT

SEQ ID NOs 51-55 are heavy chain CDR1 sequences against CTB (cloned andreference)

SEQ ID NOs 56-60 are heavy chain CDR2 sequences against CTB (cloned andreference)

SEQ ID NOs 61-63 are heavy chain CDR3 sequences against CTB (cloned andreference)

SEQ ID NOs 64-68 are J Region sequences against CTB (cloned andreference)

DETAILED DESCRIPTION OF THE INVENTION

It will be understood that particular embodiments described herein areshown by way of illustration and not as limitations of the invention.The principal features of this invention can be employed in variousembodiments without departing from the scope of the invention. Thoseskilled in the art will recognize, or be able to ascertain using no morethan routine study, numerous equivalents to the specific proceduresdescribed herein. Such equivalents are considered to be within the scopeof this invention and are covered by the claims.

The use of the word “a” or “an” when used in conjunction with the term“comprising” in the claims and/or the specification may mean “one,” butit is also consistent with the meaning of “one or more,” “at least one,”and “one or more than one.” The use of the term “or” in the claims isused to mean “and/or” unless explicitly indicated to refer toalternatives only or the alternatives are mutually exclusive, althoughthe disclosure supports a definition that refers to only alternativesand “and/or.” Throughout this application, the term “about” is used toindicate that a value includes the inherent variation of error for thedevice, the method being employed to determine the value, or thevariation that exists among the study subjects.

As used in this specification and claim(s), the words “comprising” (andany form of comprising, such as “comprise” and “comprises”), “having”(and any form of having, such as “have” and “has”), “including” (and anyform of including, such as “includes” and “include”) or “containing”(and any form of containing, such as “contains” and “contain”) areinclusive or open-ended and do not exclude additional, unrecitedelements or method steps

The term “or combinations thereof” as used herein refers to allpermutations and combinations of the listed items preceding the term.For example, “A, B, C, or combinations thereof is intended to include atleast one of: A, B, C, AB, AC, BC, or ABC, and if order is important ina particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.Continuing with this example, expressly included are combinations thatcontain repeats of one or more item or term, such as BB, AAA, MB, BBC,AAABCCCC, CBBAAA, CABABB, and so forth. The skilled artisan willunderstand that typically there is no limit on the number of items orterms in any combination, unless otherwise apparent from the context.

As a source of antibody gene segment sequences, the skilled person willalso be aware of the following available databases and resources(including updates thereof) the contents of which are incorporatedherein by reference:

The Kabat Database (G. Johnson and T. T. Wu, 2002; World Wide Web (www)kabatdatabase.com). Created by E. A. Kabat and T. T. Wu in 1966, theKabat database publishes aligned sequences of antibodies, T-cellreceptors, major histocompatibility complex (MHC) class I and IImolecules, and other proteins of immunological interest. A searchableinterface is provided by the SeqhuntII

tool, and a range of utilities is available for sequence alignment,sequence subgroup classification, and the generation of variabilityplots. See also Kabat, E. A., Wu, T. T., Perry, H., Gottesman, K., andFoeller, C. (1991) Sequences of Proteins of Immunological Interest, 5thed., NIH Publication No. 91-3242, Bethesda, Md., which is incorporatedherein by reference, in particular with reference to human gene segmentsfor use in the present invention.

KabatMan (A. C. R. Martin, 2002; World Wide Web (www)bioinforg.uk/abs/simkab.html). This is a web interface to make simplequeries to the Kabat sequence database.

IMGT (the International ImMunoGeneTics Information System®; M.-P.Lefranc, 2002; World Wide Web (www) imgt.cines.fr). IMGT is anintegrated information system that specializes in antibodies, T cellreceptors, and MHC molecules of all vertebrate species. It provides acommon portal to standardized data that include nucleotide and proteinsequences, oligonucleotide primers, gene maps, genetic polymorphisms,specificities, and two-dimensional (2D) and three-dimensional (3D)structures. IMGT includes three sequence databases (IMGT/LIGM-DB,IMGT/MHC-DB, IMGT/PRIMERDB), one genome database (IMGT/GENE-DB), one 3Dstructure database (IMGT/3Dstructure-DB), and a range of web resources(“IMGT Marie-Paule page”) and interactive tools.

V-BASE (I. M. Tomlinson, 2002; World Wide Web (www)mrc-cpe.cam.ac.uk/vbase). V-BASE is a comprehensive directory of allhuman antibody germline variable region sequences compiled from morethan one thousand published sequences. It includes a version of thealignment software DNAPLOT (developed by Hans-Helmar Althaus and WernerMüller) that allows the assignment of rearranged antibody V genes totheir closest germline gene segments.

Antibodies—Structure and Sequence (A. C. R. Martin, 2002; World Wide Web(www) bioinf.org.uk/abs). This page summarizes useful information onantibody structure and sequence. It provides a query interface to theKabat antibody sequence data, general information on antibodies, crystalstructures, and links to other antibody-related information. It alsodistributes an automated summary of all antibody structures deposited inthe Protein Databank (PDB). Of particular interest is a thoroughdescription and comparison of the various numbering schemes for antibodyvariable regions.

AAAAA (A Ho's Amazing Atlas of Antibody Anatomy; A. Honegger, 2001;World Wide Web (www) unizh.ch/˜antibody). This resource includes toolsfor structural analysis, modeling, and engineering. It adopts a unifyingscheme for comprehensive structural alignment of antibody andT-cell-receptor sequences, and includes Excel macros for antibodyanalysis and graphical representation.

WAM (Web Antibody Modeling; N. Whitelegg and A. R. Rees, 2001; WorldWide Web (www) antibody.bath.ac.uk). Hosted by the Centre for ProteinAnalysis and Design at the University of Bath, United Kingdom. Based onthe AbM package (formerly marketed by Oxford Molecular) to construct 3Dmodels of antibody Fv sequences using a combination of establishedtheoretical methods, this site also includes the latest antibodystructural information.

Mike's Immunoglobulin Structure/Function Page (M. R. Clark, 2001; WorldWide Web (www) path.cam.ac.uk/˜mrc7/mikeimages.html) These pages provideeducational materials on immunoglobulin structure and function, and areillustrated by many colour images, models, and animations. Additionalinformation is available on antibody humanization and Mike Clark'sTherapeutic Antibody Human Homology Project, which aims to correlateclinical efficacy and anti-immunoglobulin responses with variable regionsequences of therapeutic antibodies.

The Antibody Resource Page (The Antibody Resource Page, 2000; World WideWeb (www) antibodyresource.com). This site describes itself as the“complete guide to antibody research and suppliers.” Links to amino acidsequencing tools, nucleotide antibody sequencing tools, andhybridoma/cell-culture databases are provided.

Humanization bY Design (J. Saldanha, 2000; World Wide Web (www)people.cryst.bbk.ac.uk/˜ubcg07s). This resource provides an overview onantibody humanization technology. The most useful feature is asearchable database (by sequence and text) of more than 40 publishedhumanized antibodies including information on design issues, frameworkchoice, framework back-mutations, and binding affinity of the humanizedconstructs.

See also Antibody Engineering Methods and Protocols, Ed. Benny K C Lo,Methods in Molecular Biology™, Human Press. Also at World Wide Web (www)blogsua.com/pdf/antibody-engineering-methods-and-protocolsantibody-engineering-methods-and-protocols.pdf

Any part of this disclosure may be read in combination with any otherpart of the disclosure, unless otherwise apparent from the context.

All of the compositions and/or methods disclosed and claimed herein canbe made and executed without undue experimentation in light of thepresent disclosure. While the compositions and methods of this inventionhave been described in terms of preferred embodiments, it will beapparent to those of skill in the art that variations may be applied tothe compositions and/or methods and in the steps or in the sequence ofsteps of the method described herein without departing from the concept,spirit and scope of the invention. All such similar substitutes andmodifications apparent to those skilled in the art are deemed to bewithin the spirit, scope and concept of the invention as defined by theappended claims.

The following examples are put forth so as to provide those of ordinaryskill in the art with a complete disclosure and description of how tomake and use the invention, and are not intended to limit the scope ofwhat the inventors regard as their invention.

EXAMPLES Example 1

BAC Recombineering

Overall strategy: A mouse model of the invention can be achieved byinserting ˜960 kb of the human heavy chain locus containing all the V, Dand J-regions upstream of the mouse constant region and 473 kb of thehuman kappa region upstream of the mouse constant region. Alternatively,or in tandem, the human lambda region is inserted upstream of the mouseconstant region. This insertion is achieved by gene targeting in EScells using techniques well known in the art.

High fidelity insertion of intact V-D-J regions into each locus in theirnative (wild-type) configuration is suitably achieved by insertion ofhuman bacterial artificial chromosomes (BACs) into the locus. Suitablythe BACs are trimmed so that in the final locus no sequence isduplicated or lost compared to the original. Such trimming can becarried out by recombineering.

The relevant human BACs, suitably trimmed covering these loci are onaverage 90 kb in size.

In one approach the full complement of human D and J-elements as well asseven or eight human V-regions are covered by the first BACs to beinserted in the experimental insertion scheme described below. The firstBACs to be inserted in the IgH and IgK loci may contain the followingV-regions. IgH: V6-1, VII-1-1, V1-2, VIII-2-1, V1-3, V4-4, V2-5 and IgK:V4-1, V5-2, V7-3, V2-4, V1-5, V1-6, V3-7, V1-8.

Suitably the performance of each locus is assessed after the first BACinsertion using chimaeric mice and also after each subsequent BACaddition. See below for detailed description of this performance test.

Nine additional BAC insertions will be required for the IgH locus andfive for IgK to provide the full complement of human V-regions coveringall 0.96 Mb and 0.473 Mb of the IgH and IgK loci, respectively.

Not all BACs retain their wild-type configuration when inserted into theES cell genome. Thus, high density genomic arrays were deployed toscreen ES cells to identify those with intact BAC insertions (Barrett,M. T., Scheffer, A., Ben-Dor, A., Sampas, N., Lipson, D., Kincaid, R.,Tsang, P., Curry, B., Baird, K., Meltzer, P. S., et al. (2004).Comparative genomic hybridization using oligonucleotide microarrays andtotal genomic DNA. Proceedings of the National Academy of Sciences ofthe United States of America 101, 17765-17770).This screen also enablesone to identify and select against ES clones in which the ES cell genomeis compromised and thus not able to populate the germ line of chimericanimals. Other suitable genomic tools to facilitate this assessmentinclude sequencing and PCR verification.

Thus in one aspect the correct BAC structure is confirmed before movingto the next step.

It is implicit from the description above that in order to completelyengineer the loci with 90 kb BACs, it is necessary to perform a minimumof 10 targeting steps for IgH and 5 steps for the IgK. Mice with an IgLlocus can be generated in a similar manner to the IgK locus. Additionalsteps are required to remove the selection markers required to supportgene targeting. Since these manipulations are being performed in EScells in a step-wise manner, in one aspect germ line transmissioncapacity is retained throughout this process.

Maintaining the performance of the ES cell clones through multiplerounds of manipulation without the need to test the germ line potentialof the ES cell line at every step may be important in the presentinvention. The cell lines currently in use for the KOMP and EUCOMMglobal knockout projects have been modified twice prior to their use forthis project and their germ line transmission rates are unchanged fromthe parental cells (these lines are publicly available, see World WideWeb (www) komp.org and World Wide Web (www) eucomm.org). This cell line,called JM8, can generate 100% ES cell-derived mice under publishedculture conditions (Pettitt, S. J., Liang, Q., Rairdan, X. Y., Moran, J.L., Prosser, H. M., Beier, D. R., Lloyd, K. C., Bradley, A., andSkarnes, W. C. (2009). Agouti C57BL/6N embryonic stem cells for mousegenetic resources. Nature Methods). These cells have demonstratedability to reproducibly contribute to somatic and germ line tissue ofchimaeric animals using standard mouse ES cell culture conditions. Thiscapability can be found with cells cultured on a standard feeder cellline (SNL) and even feeder-free, grown only on gelatine-coated tissueculture plates. One particular sub-line, JM8A3, maintained the abilityto populate the germ line of chimeras after several serial rounds ofsub-cloning. Extensive genetic manipulation via, for example, homologousrecombination—as would be the case in the present invention—cannotcompromise the pluripotency of the cells. The ability to generatechimeras with such high percentage of ES cell-derived tissue has otheradvantages. First, high levels of chimerism correlates with germ linetransmission potential and provide a surrogate assay for germ linetransmission while only taking 5 to 6 weeks. Second, since these miceare 100% ES cell derived the engineered loci can be directly tested,removing the delay caused by breeding. Testing the integrity of the newIg loci is possible in the chimera since the host embryo will be derivedfrom animals that are mutant for the RAG-1 gene as described in the nextsection.

Another cell line that may be used is an HPRT-ve cell line, such asAB2.1, as disclosed in Ramirez-Solis R, Liu P and Bradley A, “Chromosomeengineering in mice,” Nature, 1995; 378; 6558; 720-4.

RAG-1 complementation: While many clones will generate 100% ES derivedmice some will not. Thus, at every step mice are generated in aRAG-1-deficient background. This provides mice with 100% ES-derived B-and T-cells which can be used directly for immunization and antibodyproduction. Cells having a RAG-2 deficient background, or a combinedRAG-1/RAG-2 deficient background may be used, or equivalent mutations inwhich mice produce only ES cell-derived B cells and/or T cells.

In order that only the human-mouse IgH or IgK loci are active in thesemice, the human-mouse IgH and IgK loci can be engineered in a cell linein which one allele of the IgH or IgK locus has already beeninactivated. Alternatively the inactivation of the host Ig locus, suchas the IgH or IgK locus, can be carried out after insertion.

Mouse strains that have the RAG-1 gene mutated are immunodeficient asthey have no mature B- or T-lymphocytes (U.S. Pat. No. 5,859,307). T-and B-lymphocytes only differentiate if proper V(D)J recombinationoccurs. Since RAG-1 is an enzyme that is crucial for this recombination,mice lacking RAG-1 are immunodeficient. If host embryos are geneticallyRAG-1 homozygous mutant, a chimera produced by injecting such an embryowill not be able to produce antibodies if the animal's lymphoid tissuesare derived from the host embryo. However, JM8 cells and AB2.1 cells,for example, generally contribute in excess of 80% of the somatictissues of the chimeric animal and would therefore usually populate thelymphoid tissue. JM8 cells have wild-type RAG-1 activity and thereforeantibodies produced in the chimeric animal would be encoded by theengineered JM8 ES cell genome only. Therefore, the chimeric animal canbe challenged with an antigen by immunization and subsequently produceantibodies to that antigen. This allows one skilled in the art to testthe performance of the engineered human/mouse IgH and IgK loci asdescribed in the present invention. See FIGS. 19 and 20.

One skilled in the art would use the chimeric animal as described todetermine the extent of antibody diversity (see e.g. Harlow, E. & Lane,D. 1998, 5th edition, Antibodies: A Laboratory Manual, Cold SpringHarbor Lab. Press, Plainview, N.Y.). For example, the existence in thechimeric animal's serum of certain antibody epitopes could beascertained by binding to specific anti-idiotype antiserum, for example,in an ELISA assay. One skilled in the art could also sequence thegenomes of B-cell clones derived from the chimeric animal and comparesaid sequence to wild-type sequence to ascertain the level ofhypermutation, such hypermutation indicative of normal antibodymaturation.

One skilled in the art would also use said chimeric animal to examineantibody function wherein said antibodies are encoded from theengineered Ig loci (see e.g. Harlow, E. & Lane, D. 1998, 5^(th) edition,Antibodies: A Laboratory Manual, Cold Spring Harbor Lab. Press,Plainview, N.Y.). For example, antisera could be tested for binding anantigen, said antigen used to immunize the chimeric animal. Such ameasurement could be made by an ELISA assay. Alternatively, one skilledin the art could test for neutralization of the antigen by addition ofthe antisera collected from the appropriately immunized chimeric animal.

It is well known to those skilled in the art that positive outcomes forany of these tests demonstrate the ability of the engineered Ig loci,the subject of the instant invention, to encode antibodies with humanvariable regions and mouse constant regions, said antibodies capable offunctioning in the manner of wild-type antibodies.

Experimental Techniques: Recombineering for the production of vectorsfor use in homologous recombination in ES cells is disclosed in, forexample, WO9929837 and WO0104288, and the techniques are well known inthe art. In one aspect the recombineering of the human DNA takes placeusing BACs as a source of said human DNA. Human BAC DNA will be isolatedusing QIAGEN®, BAC purification kit. The backbone of each human BAC willbe modified using recombineering to the exact same or similarconfiguration as the BAC already inserted into the mouse IgH region. Thegenomic insert of each human BAC will be trimmed using recombineering sothat once the BACs are inserted, a seamless contiguous part of the humanV(D)J genomic region will form at the mouse IgH or IgK locus. BAC DNAtransfection by electroporation and genotyping will be performedaccordingly to standard protocols (Prosser, H. M., Rzadzinska, A. K.,Steel, K. P., and Bradley, A. (2008). “Mosaic complementationdemonstrates a regulatory role for myosin Vila in actin dynamics ofstereocilia.” Molecular and Cellular Biology 28, 1702-1712;Ramirez-Solis, R., Davis, A. C., and Bradley, A. (1993). “Gene targetingin embryonic stem cells.” Methods in Enzymology 225, 855-878).Recombineering will be performed using the procedures and reagentsdeveloped by Pentao Liu and Don Court's laboratories (Chan, W.,Costantino, N., Li, R., Lee, S. C., Su, Q., Melvin, D., Court, D. L.,and Liu, P. (2007). “A recombineering based approach for high-throughputconditional knockout targeting vector construction.” Nucleic AcidsResearch 35, e64).

These and other techniques for gene targeting and recombination ofBAC-derived chromosomal fragments into a non-human mammal genome, suchas a mouse are well-known in the art and are disclosed in, for example,in World Wide Web (www) eucomm.org/information/targeting and World WideWeb (www) eucomm.org/information/publications.

Cell culture of C57BL/6N-derived cell lines, such as the JM8 male EScells will follow standard techniques. The JM8 ES cells have been shownto be competent in extensively contributing to somatic tissues and tothe germline, and are being used for large mouse mutagenesis programs atthe Sanger Institute such as EUCOMM and KOMP (Pettit (S. J., Liang, Q.,Rairdan, X. Y., Moran, J. L., Prosser, H. M., Beier, D. R., Lloyd, K.C., Bradley, A., and Skarnes, W. C. (2009). “Agouti C57BL/6N embryonicstem cells for mouse genetic resources.” Nature Methods). JM8 ES cells(1.0×10⁷) will be electroporated (500 μF, 230V; Bio-Rad®) with 10 μgI-Scel linearized human BAC DNA. The transfectants will be selected witheither Puromycin (3 μg/ml) or G418 (150 μg/ml). The selection will begineither 24 hours (with G418) or 48 hours (with Puromycin) postelectroporation and proceed for 5 days. 10 μg linearized human BAC DNAcan yield up to 500 Puromycin or G418 resistant ES cell colonies. Theantibiotic resistant ES cell colonies will be picked into 96-well cellculture plates for genotyping to identify the targeted clones.

Once targeted mouse ES cell clones are identified, they will be analyzedby array Comparative Genomic Hybridization (CGH) for total genomeintegrity (Chung, Y. J., Jonkers, J., Kitson, H., Fiegler, H., Humphray,S., Scott, C., Hunt, S., Yu, Y., Nishijima, I., Velds, A., et al.(2004). “A whole-genome mouse BAC microarray with 1-Mb resolution foranalysis of DNA copy number changes by array comparative genomichybridization.” Genome research 14, 188-196.and Liang, Q., Conte, N.,Skarnes, W. C., and Bradley, A. (2008). “Extensive genomic copy numbervariation in embryonic stem cells.” Proceedings of the National Academyof Sciences of the United States of America 105, 17453-17456). ES cellsthat have abnormal genomes do not contribute to the germline of thechimeric mice efficiently. BAC integrity will be examined byPCR-amplifying each known functional V gene in the BAC. For example, inone approach the first human BAC chosen for the IgH locus has 6functional V genes. To confirm the integrity of this BAC for thepresence of these 6 IGH V genes, at least 14 pairs of PCR primers willbe designed and used to PCR-amplify genomic DNA from the targeted EScells. The human wild-type size and sequence of these fragments willensure that the inserted BAC has not been rearranged.

More detailed CGH will also confirm the integrity of the inserted BACs.For example, one skilled in the art could use an oligo aCGH platform,which is developed by Agilent Technologies, Inc. This platform not onlyenables one to study genome-wide DNA copy number variation at highresolution (Barrett, M. T., Scheffer, A., Ben-Dor, A., Sampas, N.,Lipson, D., Kincaid, R., Tsang, P., Curry, B., Baird, K., Meltzer, P.S., et al. (2004). “Comparative genomic hybridization usingoligonucleotide microarrays and total genomic DNA.” Proceedings of theNational Academy of Sciences of the United States of America 101,17765-17770), but permit examination of a specific genome region usingcustom designed arrays. Comparing the traditional aCGH techniques whichrely on cDNA probes or whole BAC probes, the 60-mer oligonucleotidesprobes can ensure specific hybridization and high sensitivity andprecision that is needed in order to detect the engineered chromosomealterations that were made. For example, oligos designed to hybridize atregular intervals along the entire length of the inserted BAC woulddetect even quite short deletions, insertions or other rearrangements.Also, this platform provides the greatest flexibility for customizedmicroarray designs. The targeted ES cell genomic DNA and normal humanindividual genomic DNA will be labelled separately with dyes andhybridized to the array. Arrays slides will be scanned using an AglientTechnologies DNA microarray scanner. Reciprocal fluorescence intensitiesof dye Cy5 and dye Cy3 on each array image and the log 2 ratio valueswill be extracted by using Bluefuse software (Bluegnome). Spots withinconsistent fluorescence patterns (“confidence”<0.29 or “quality”=0)will be excluded before normalizing all log 2 ratio values. Within anexperiment, Log 2 ratio between −0.29 and +0.29 for the signal from anyoligo probe are regarded as no copy number change. The log 2 ratiothreshold for “Duplication” is usually >0.29999, and for deletion is<0.29999.

Once the first human BAC is inserted into the mouse IgH locus andconfirmed to be in its intact, native configuration, the FRT-flanked BACbackbone will be excised by using Flp site-specific recombinase. Ifregular Flp-catalyzed FRT recombination is not high enough, one can useFlo, an improved version of Flpo recombinase which in certain tests is3-4 times more efficient than the original Flp in ES cells. After theBAC backbone is excised, ES cells will become sensitive to Puromycin (orG418) and resistant to FIAU (for loss of the TK cassette). The excisionevents will be further characterized by PCR amplification of thejunction fragment using human genomic DNA primers. These FRT-flanked BACbackbone-free ES cells will be used for the next round of human BACinsertion and for blastocyst injection.

Targeting of the genome of an ES cell to produce a transgenic mouse maybe carried out using a protocol as explained by reference to theattached FIGS. 1-18.

FIG. 1 illustrates three basic backbone vectors; an initiating cassetteand 2 large insert vectors 1 and 2 respectively. The initiating cassettecomprises sequences homologous to the desired site of insertion into themouse genome, those sites flanking a selectable marker and stufferprimer sequence for PCR based genotyping to confirm correct insertion ofBACs. The Stuffer-primer sequence provides the basis for genotyping eachBAC addition step. This sequence is considered to provide a robust wellvalidated sequence template for PCR primer and may be located at theIScel site, ideally ˜1 kb from the BAC insert.

The large insert vectors comprise human DNA on plasmids with selectablemarkers and a unique restriction site for linearisation of the plasmidto aid in homologous recombination into the genome of the ES cell.

FIG. 2 illustrates insertion of an initiating cassette into the mousegenome by Homologous recombination between the mouse J4 and C alphaexons. Puromycin selection allows identification of ES cells withinsertion of the cassette. pu(Delta)tk is a bifunctional fusion proteinbetween puromycin N-acetyltransferase (Puro) and a truncated version ofherpes simplex virus type 1 thymidine kinase (DeltaTk). Murine embryonicstem (ES) cells transfected with pu(Delta)tk become resistant topuromycin and sensitive to1-(-2-deoxy-2-fluoro-1-beta-D-arabino-furanosyl)-5-iodouracil (FIAU).Unlike other HSV1 tk transgenes, puDeltatk is readily transmittedthrough the male germ line. Thus pu(Delta)tk is a convenientpositive/negative selectable marker that can be widely used in many EScell applications.

FIG. 3 illustrates targeting of the large insert vector 1 to the mouseES cell genome. Linearisation of the vector is made at the same positionas the stuffer primer sequence which allows for a gap repair genotypingstrategy, well known in the art—see Zheng et al NAR 1999, Vol 27, 11,2354-2360. In essence, random insertion of the targeting vector into thegenome will not ‘repair’ the gap whereas a homologous recombinationevent will repair the gap. Juxtaposition of appropriate PCR primersequences allows colonies to be screened individually for a positive PCRfragment indicating proper insertion. Positive selection using G418allows for identification of mouse ES cells containing the neo selectionmarker. PCR verification can be made of all critical V, D and J regions.Array comparative genomic hybridization can be used to validate the BACstructure.

FIG. 4 illustrates the puro-delta-tk cassette and the BAC plasmidbackbone is deleted using Flpe and select in FIAU. Since Flpe worksinefficiently in mouse ES cells (5% deletion with transient Flpeexpression), it is expected that in most cases, the recombination occursbetween the two FRT sites flanking the BAC backbone. Flpo can also betested to find out the recombination efficiency between two FRT sitesthat are 10 kb away.

Given that the FRT deletion step is selectable it is possible to poolFIAU resistant clones and proceed immediately to the next step inparallel with clonal analysis. Alternatively it may be desirable to showby short range PCR that the human sequences are now adjacent to those ofthe mouse as shown (Hu-primer 1 and Mo-primer)

At this stage a 200 kb human locus will have been inserted.

FIG. 5 illustrates a second large insert vector is targeted into the EScell chromosome. The human BAC is targeted to the mouse IgH locus usingthe same initiation cassette insertion followed by IScel BAClinearization, BAC targeting to the initiation cassette and gap-repairgenotyping strategy. Verification of the BAC insertion is carried out asbefore.

FIG. 6 illustrates the FRTY flanked BAC backbone of large insert vector2 and the neo marker are deleted via Flpo. Note that this is notselectable, thus it will be necessary for clonal analysis at this point.This will enable confirmation of the juxtaposition of the human 2 insertwith human 1 and other validation efforts.

At this stage a ˜200 kb human locus will have been inserted.

FIG. 7 illustrates the next large insert vector targeted to the mouseIgH locus. The pu-delta TK cassette is then removed, as for FIG. 4. Theprocess can be repeated to incorporate other BACs.

FIG. 8 illustrates the final predicted ES cell construct.

FIGS. 9-18 provide a further level of detail of this process.

Example 2

Site-Specific Recombination

In a further method of the invention site specific recombination canalso be employed. Site-specific recombination (SSR) has been widely usedin the last 20-years for the integration of transgenes into definedchromosomal loci. SSR involves recombination between homologous DNAsequences.

The first generation of SSR-based chromosomal targeting involvedrecombination between (i) a single recombination target site (RT) suchas loxP or FRT in a transfected plasmid with (ii) a chromosomal RT siteprovided by a previous integration. A major problem with this approachis that insertion events are rare since excision is always moreefficient than insertion. A second generation of SSR called RMCE(recombinase-mediated cassette exchange) was introduced by Schlake andBode in 1994 (Schlake, T.; J. Bode (1994). “Use of mutatedFLP-recognition-target-(FRT-)sites for the exchange of expressioncassettes at defined chromosomal loci”. Biochemistry 33: 12746-12751).Their method is based on using two heterospecific and incompatible RTsin the transfected plasmid which can recombine with compatible RT siteson the chromosome resulting in the swap of one piece of DNA foranother—or a cassette exchange. This approach has been successfullyexploited in a variety of efficient chromosomal targeting, includingintegration of BAC inserts of greater than 50 kb (Wallace, H. A. C. etal. (2007). “Manipulating the mouse genome to engineering precisefunctional syntenic replacements with human sequence”. Cell 128:197-209; Prosser, H. M. et al. (2008). “Mosaic complementationdemonstrates a regulatory role for myosin Vila in actin dynamics ofStereocilia”. Mol. Cell. Biol. 28: 1702-12).

The largest insert size of a BAC is about 300-kb and therefore thisplaces an upper limit on cassette size for RMCE.

In the present invention a new SSR-based technique called sequentialRMCE (SRMCE) was used, which allows continuous insertion of BAC insertsinto the same locus.

The method comprises the steps of

-   -   1 insertion of DNA forming an initiation cassette (also called a        landing pad herein) into the genome of a cell;    -   2 insertion of a first DNA fragment into the insertion site, the        first DNA fragment comprising a first portion of a human DNA and        a first vector portion containing a first selectable marker or        generating a selectable marker upon insertion;    -   3 removal of part of the vector DNA;    -   4 insertion of a second DNA fragment into the vector portion of        the first DNA fragment, the second DNA fragment containing a        second portion of human DNA and a second vector portion, the        second vector portion containing a second selectable marker, or        generating a second selectable marker upon insertion;    -   5 removal of any vector DNA to allow the first and second human        DNA fragments to form a contiguous sequence; and    -   6 iteration of the steps of insertion of a part of the human        V(D)J DNA and vector DNA removal, as necessary, to produce a        cell with all or part of the human VDJ or VJ region sufficient        to be capable of generating a chimaeric antibody in conjunction        with a host constant region,        wherein the insertion of at least one DNA fragment uses site        specific recombination.

In one specific aspect the approach utilizes three heterospecific andincompatible loxP sites. The method is comprised of the steps asfollows, and illustrated in FIGS. 22-26:

-   -   1. Targeting a landing pad into the defined locus. An entry        vector containing an HPRT mini-gene flanked by inverted piggyBac        (PB) ITRs is targeted into defined region (for example: a region        between IGHJ and Eμ or IGKJ and Eκ or IGLC1 and Eλ3-1) to serve        as a landing pad for BAC targeting. The HPRT mini-gene is        comprised of two synthetic exons and associated intron. The 5′        HPRT exon is flanked by two heterospecific and incompatible loxP        sites (one wild-type and the other a mutated site, lox5171) in        inverted orientation to each other (FIG. 22). These two loxP        sites provide recombination sites for the BAC insertion through        RMCE.    -   2. Insertion of the 1^(st) modified BAC into the targeted        landing pad. The 1^(st) BAC has a length of DNA to be inserted        into the genome flanked by engineered modifications. The 5′        modification (loxP—neo gene—lox2272—PGK promoter—PB 5′LTR) and        3′ modification (PB3′LTR—puroΔTK gene—lox5171) is depicted in        FIG. 23 along with the relative orientations of the lox sites        and PB LTRs. With transient CRE expression from a        co-electroporated vector, the DNA sequence would be inserted        into the defined locus through RMCE. The cells in which a        correct insertion has occurred can be selected as follows: (i)        Puromycin-resistance (the puroΔTK gene has acquired a        promoter—“PGK”—from the landing pad), (ii) 6TG-resistance (the        HPRT mini-gene has been disrupted), and (iii) G418-resistance        (selects for any insertion via the 5′ region PGK-neo        arrangement). Any combination of these selection regimes can be        used. G418- and 6TG-resistance select for correct events on the        5′ end while puro-resistance selects for correct events on the        3′ end.    -   3. Curing (removing) the 3′ modification of the 1^(st)        insertion. A properly inserted 1^(st) BAC results the 3′ end        having a puroΔTK gene flanked by inverted PB LTRs (FIG.        24)—essentially a proper transposon structure. This transposon        can then be removed by the transient expression of the piggyBac        transposase (from an electroporated vector). Cells with the        correct excision event can be selected by FIAU resistance—ie, no        thymidine kinase activity from the puroΔTK gene. This completely        removes the 3′ modification leaving no trace nucleotides.    -   4. Insertion of a 2^(nd) modified BAC into the 5′ end of 1^(st)        insertion. The 2^(nd) BAC has a length of DNA to be inserted        into the genome (usually intended to be contiguous with the DNA        inserted with the 1^(st) BAC) flanked by engineered        modifications. The 5′ modification (loxP—HPRT mini gene 5′        portion—lox5171—PGK promoter—PB5′LTR) and 3′ modification        (PB3′LTR—puroΔTK—lox2272) is depicted in FIG. 25 along with the        relative orientations of the lox sites and PB LTRs. With        transient CRE expression from a co-electroporated vector, the        DNA sequence would be inserted into the defined locus through        RMCE. The cells in which a correct insertion has occurred can be        selected as follows: (i) HAT-resistance (the HPRT mini-gene is        reconstituted by a correct insertion event, ie: the 5′ and 3′        exon structures are brought together), and (ii)        puromycin-resistance (puroΔTK gene has acquired a        promoter—“PGK”—from the landing pad).    -   5. Curing (removing) the 3′ modification of the 2^(nd)        insertion. A properly inserted 2^(nd) BAC results the 3′ end        having a puroΔTK gene flanked by inverted PB LTRs (FIG.        26)—essentially a proper transposon structure, exactly analogous        to the consequence of a successful 1^(st) BAC insertion. And        therefore this transposon can likewise be removed by the        transient expression of the piggyBac transposase (from an        electroporated vector). Cells with the correct excision event        can be selected by FIAU resistance—ie, no thymidine kinase        activity from the puroΔTK gene. This completely removes the 3′        modification leaving no trace nucleotides.    -   6. After curing of the 3′ modification of the 2^(nd) BAC        insertion, the landing pad becomes identical to the original.        This entire process, steps 2 through 5, can be repeated multiple        times to build up a large insertion into the genome. When        complete, there are no residual nucleotides remaining other than        the desired insertion.

With the insertion of an odd number of BACs into the Ig loci, theendogenous VDJ or VJ sequences can be inactivated through an inversionvia chromosomal engineering as follows (see FIGS. 27-29):

-   -   1. Targeting a “flip-over” cassette into a 5′ region 10 to 40        megabases away from the endogenous VDJ or VJ. The flip-over        vector (PB3′LTR—PGK promoter—HPRT mini gene 5′        portion—loxP—puroΔTK—CAGGS promoter—PB3′LTR) is depicted in FIG.        27 along with the relative orientations of the lox sites and PB        LTRs.    -   2. Transient CRE expression will result in recombination between        the loxP site in the “flip-over” cassette and the loxP site in        the 5′ modification. This 5′ modification is as described in        Steps 2 and 3 above—essentially the modification resulting from        insertion of an odd number of BACs, after the 3′ modification        has been cured. The loxP sites are inverted relative to one        another and therefore the described recombination event results        in an inversion as depicted in FIG. 28. Cells with the correct        inversion will be HAT-resistance since the HPRT mini-gene is        reconstituted by a correct inversion.    -   3. A correct inversion also leaves two transposon structures        flanking the “flip-over” cassette and the 5′ modification. Both        can be excised with transient piggyBAC transposase expression,        leaving no remnant of either modification (FIG. 29). Cells with        the correct excisions can be selected as follows: (i)        6TG-resistance (the HPRT mini-gene is deleted) and (ii)        FIAU-resistance (the puroΔTK gene is deleted). An inversion as        described in the Ig loci would move the endogenous IGH-VDJ or        IGK-VJ region away from the Eμ or Eκ enhancer region,        respectively, and lead to inactivation of the endogenous IGH-VDJ        or IGK-VJ regions.

The methods of insertion of the invention suitably provide one or moreof:

-   -   Selection at both 5′ and 3′ ends of the inserted DNA fragment;    -   Efficient curing of the 3′ modification, preferably by        transposase mediated DNA excision;    -   Inactivation of endogenous IGH or IGK activity through an        inversion; and    -   Excision of modifications, leaving no nucleotide traces        remaining in the chromosome.

Example 3

Insertion of a Test Vector into the Genome at a Defined Location

Proof of concept of the approach is disclosed in FIG. 30. In FIG. 30 alanding pad as shown in FIG. 22 was inserted into the genome of a mouseby homologous recombination, followed by insertion of the R21 plasmidinto that landing pad via cre-mediated site specific recombination. Theinsertion event generated a number of general insertion events, 360 G418resistant colonies, of which ˜220 were inserted into the desired locus,as demonstrated by disruption of the HRPT minilocus.

The R21 vector mimicks the 1^(st) BAC insertion vector at the 5′ and 3′ends, including all selection elements and recombinase target sites. Inplace of BAC sequences, there is a small ‘stuffer’ sequence. This vectorwill both test all the principals designed in the invention and alloweasy testing of the results in that PCR across the stuffer is feasibleand therefore allows both ends of the insertion to be easily tested. R21was co-electroporated with a cre-expressing vector into the ES cellsharbouring the landing pad in the IGH locus. Four sets of transformedcells were transfected in parallel and then placed under differentselection regimes as indicated in FIG. 30. G418 selection (neo geneexpression) resulted in the largest number of colonies due to therebeing no requirement for specific landing-pad integration. Anyintegration of R21 into the genome will provide neo expression leadingto G418-resistance. Puro selection resulted in a similar colony numberto Puro+6TG or G418+6TG, suggesting that the stringency of Puroselection is due to the PuroΔTK lacking a promoter in the vector. Puroexpression is only acquired when an integration occurs near a promoterelement—in this design most likely specifically in the landing pad.These conclusions are supported by the results from junction PCR whichis shown in FIG. 31.

The next step in the invention is to ‘cure’ the 3′ end of the integratedBAC vector, leaving a seamless transition between the insertion and theflanking genome. This curing was demonstrated by expanding an individualclone from above (R21 inserted into the landing pad) and expressingpiggyBac recombinase in this clone via transfection of an expressingplasmid. FIAU was used to select colonies in which the 3′ modificationwas excised—ie, through loss of the ‘PGK-puroΔTK’ element between thepiggyBac terminal repeats. Fifty such clones resulted from atransfection of 10⁶ cells; of these six were tested for the expectedgenomic structure. Successful curing resulted in positive PCR betweenthe primer set labelled “3” in FIG. 32. Of the 6 clones, 4 had correctexcisions, 1 clone remained in the original configuration and 1 otherhad a deletion.

These data demonstrate iterative insertion of DNA into a landing pad ata defined genomic locus using the approaches outlined above.

Example 4

Insertion of Large Parts of the Human IG Loci into Defined Positions inthe Mouse Genome

Example 3 demonstrated that the design of the claimed invention wascapable of providing for the insertion of a test vector into the genomeat a defined location, in this case the R21 vector into the mouse IGHlocus. The use of the appropriate selection media and the expression ofcre-recombinase resulted in a genomic alteration with the predictedstructure.

The same design elements described in this invention were built into the5′ and 3′ ends of a BAC insert. Said insert comprised human sequencesfrom the IGH locus and was approximately 166-kb. This engineered BAC waselectroporated along with a cre-expressing plasmid DNA into mouse EScells harbouring the landing pad at the mouse IGH locus. The transfectedcell population was grown in puro-containing media to select forappropriate insertion events.

Seven resulting clones were isolated and further analysed. The expectedrecombination event and resulting structure are depicted in FIG. 33.Based upon data from the R21 experiment outlined in Example 3, astringent selection for correct clones was expected when the transfectedpopulation was selected in puro-containing media. This is because thepuro-coding region requires a promoter element and this ispreferentially supplied by the landing pad after recombination.Accordingly, the majority of the 7 isolated clones had insertedcorrectly into the genome at the landing pad as determined by thediagnostic PCR. The primers for diagnosing a correct insertion aredepicted in FIG. 33. Correct junctions are present in the genome if a610-bp fragment is amplified between primers ‘A’ and ‘X’ and a 478-bpfragment is amplified between primers ‘Y’ and ‘B’ (FIGS. 33 and 34).Note that there are amplified fragments between ‘A’ and ‘1’ primers and‘2’ and ‘B’ primers indicating the presence of parental genome (that is,the landing pad alone). These result from parental cells presentinternally in the cell colonies under puro-selection that escape theselection due to the geometry of a colony. After passaging the colonythrough puro-containing media, these parental junction fragmentsdisappear indicating that the parental cells are removed from thepopulation. In addition, all the clones were shown to be resistant to6-TG as expected if the HPRT gene is inactivated by the correctinsertion event.

These data indicate that the disclosed strategy for inserting largeparts of the human IG loci into defined positions in the mouse genomewill enable the construction of a mouse with a plurality of the variableregions of human IG regions upstream of the mouse constant regions asdescribed.

Example 5

Inserted Loci are Functional in Terms of Gene Rearrangement, JunctionalDiversity as Well as Expression

Bacterial artificial chromosomes (BACs) were created, wherein the BACshad inserts of human Ig gene segments (human V, D and/or J genesegments). Using methods described herein, landing pads were used in amethod to construct chimaeric Ig loci in mouse embryonic stem cells (EScells), such that chimaeric IgH and IgK loci were provided in whichhuman gene segments are functionally inserted upstream of endogenousconstant regions. To test if the human IgH-VDJ or IgK-VJ gene segmentsin the chimaera mice derived from human BAC-inserted ES cell clonesappropriately rearrange and express, RT-PCR was performed for the RNAsamples of white blood cells from those mice with the primer pairs ofhuman variable (V) region and mouse constant (C) region. The sequencesof oligos are shown as follows (Table 1). Each V oligo is paired with Coligo (HV with Cμ; KV with Cκ) for PCR reaction.

TABLE 1 Oligo Sequence HV2-5 AGATCACCTTGAAGGAGTCTGGTCC (SEQ ID NO 7)HV4-4 TGGTGAAGCCTTCGGAGACCCTGTC (SEQ ID NO 8) HV1-3CACTAGCTATGCTATGCATTGGGTG (SEQ ID NO 9) HV1-2ATGGATCAACCCTAACAGTGGTGGC (SEQ ID NO 10) HV6-1GGAAGGACATACTACAGGTCCAAGT (SEQ ID NO 11) CμTAGGTACTTGCCCCCTGTCCTCAGT (SEQ ID NO 12) KV1-9AGCCCAGTGTGTTCCGTACAGCCTG (SEQ ID NO 13) KV1-8ATCCTCATTCTCTGCATCTACAGGA (SEQ ID NO 14) KV1-6GGTAAGGATGGAGAACACTGGCAGT (SEQ ID NO 15) KV1-5TTAGTAGCTGGTTGGCCTGGTATCA (SEQ ID NO 16) CκCTTTGCTGTCCTGATCAGTCCAACT (SEQ ID NO 17)

Using the one-step formulation of SuperScript™ III One-Step RT-PCRSystem with Platinum® Taq High Fidelity (Invitrogen™; World Wide Web(www) invitrogen.com/site/us/en/home/

References/protocols/nucleic-acid-amplification-and-expression-profiling/pcr-protocol/superscript-3-one-step-rt-per-system-with-platinum-taq-high-fidelity.html#prot3),both cDNA synthesis and PCR amplification were achieved in a single tubeusing gene-specific primers and target RNAs.

The RT-PCR results showed most of the human IGH-VDJ or IGK-VJ genesegments appropriately rearrange and express in the chimaera mice. Toinvestigate the details about the diversity generated from VDJ/VJrearrangement, those specific RT-PCR fragments were cloned into a commonvector for sequencing.

Sequencing results indicate that JH, DH, and Jκ usages (FIG. 35 and FIG.36) are similar to human results. In addition, the results from theIGH-VDJCμ transcripts show that the range and mean of CDR-H3 length(FIG. 37) are similar to that observed in human. The junctionaldiversity generated from exonuclease and nucleotide addition activities(FIG. 38) was also observed. The IGH rearrangement possessed a higherfrequency of these activities compared to the IGK one. These datasuggest that the inserted loci are functional in terms of generearrangement, junctional diversity as well as expression.

Example 6

Productive VJ Rearrangement and Somatic Hypermutation can be Obtained

FIG. 41 shows an analysis of kappa mRNA from mice B-cells bearingrearranged VJ, the VJ having been rearranged from human germline kappaV1-8 and J1, and demonstrates that both that productive VJ rearrangementand somatic hypermutation can be obtained, the latter as seen from thechanges in antibodies encoded by mRNA with respect to the germlinesequences. The same is displayed for V1-6 and J1 in FIG. 42.Importantly, the recombination eliminates stop codons that are encodedby the combination of (unmutated) human germline gene segments, therebyallowing for antibody-encoding mRNA sequences. FIG. 43 demonstrates thatinserted human kappa V1-5 J1 and V1-5 J4 can produce functional codingsequences in vivo and junctional diversity.

Example 7

Inactivation of Use of Endogenous IGHV Gene Segments for ExpressedRearranged Heavy Chain by Inversion

Introduction

A 5′-RACE Cμ-specific library was generated from the splenic Blymphocytes of transgenic mice, denoted S1 mice. These mice comprisetransgenic heavy chain loci, each locus containing the six most 3′functional human V_(H) gene segments (V_(H)2-5, 7-4-1, 4-4, 1-3, 1-2,6-1), and all the human D and J_(H) gene segments (comprising functionalhuman D gene segments D1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 1-7, 2-8, 3-9,5-12, 6-13, 2-15, 3-16, 4-17, 6-19, 1-20, 2-21, 3-22, 6-25, 1-26 and7-27; and functional human J gene segments J1, J2, J3, J4, J5 and J6)inserted into the endogenous heavy chain locus between endogenous IGHJ4and Eta (mouse chromosome 12: between coordinates 114666435 and114666436). The human DNA was obtained from a bacterial artificialchromosome (BAC) containing the sequence of human chromosome 14 fromcoordinate 106328951 to coordinate 106494908. Further details on theconstruction of transgenic antibody loci using sRMCE is given elsewhereherein and in WO2011004192 (which is incorporated herein by reference).4×96-well plates of clones were randomly picked for sequencing todetermine the usage of the gene segments. All detected immunoglobulinheavy chains were rearranged from mouse V_(H) or human V_(H) with humanD-J_(H). No mouse D and J_(H) segments were detected in rearrangedproducts (FIG. 44).

This result indicates that insertion of human V_(H)-D-J_(H) genesegments into an endogenous locus between the last endogenous J region(in this case, J_(H)4) and the Eμ enhancer effectively inactivates theuse of endogenous D and J_(H) gene segments for expressed rearrangedimmunoglobulin heavy chains.

The ratio of mouse V_(H) to human V_(H) usage was around 3 to 1 (FIG.45). To completely eliminate mouse V_(H) use for antibody generation,the endogenous mouse V_(H)-D-J_(H) was inverted and moved to a distantregion of the same chromosome. The rearrangement of mouse V_(H)s tohuman D-J_(H) segments was totally blocked by effects of inversion anddistance from the heavy chain locus.

The inversion strategy included three steps: (a) targeting of aninversion cassette, (b) inversion of endogenous VDJ and (c) excision ofmarkers (FIG. 46).

-   -   (a) Targeting of the inversion cassette:

The inversion cassette consists of four components: a CAGGSpromoter-driven puromycin-resistant-delta-thymidine kinase (puroΔtk)gene, a 5′ HPRT gene segment under the PGK promoter control, a loxP sitebetween them and inversely oriented to another loxP site already in theheavy chain locus, and two flanking piggyback LTRs (PB3′LTRs). Theinversion targeting cassette was inserted to a region that is 5′ anddistant to the endogenous IGH locus at chromosome 12 as shown in FIG.46. The targeted ES clones were identified and confirmed by PCR.

-   -   (b) Inversion:

Following the insertion, transient expression of cre from a transfectedplasmid resulted in inversion of a section of chromosome 12 fragmentincluding the endogenous V_(H)-D-J_(H) locus and intervening sequencesthrough recombination of two inverted loxP sites, ie, those in theinversion cassette and the landing pad for the BAC insertionrespectively. The invertants were selected by HAT and confirmed byjunction PCRs cross the two recombined loxP sites.

-   -   (c) Excision of markers:

The inversion rearranged the relative orientation of the PB3′LTRs fromthe inversion cassette and PB5′LTR from the landing pad to generate twopiggyBac transposon structures flanking the inverted region. Withtransient expression of piggyBac transposase (PBase), these twotransposons were excised from the chromosome (and thus the mouse cellgenome). The cured ES clones were selected by1-(-2-deoxy-2-fluoro-1-b-D-arabinofuranosyl)-5-iodouracil (FIAU) and6TG, and confirmed by junction PCRs cross the excised regions.

Methods

Tissue Culture:

The procedures for ES cell culture, electroporation and drug selectionhave been described previously (Ramirez-Solis, R., A. C. Davis, and A.Bradley. 1993. Gene targeting in mouse embryonic stem cells. MethodsEnzymol. 225:855-878).

Targeting of the Locus for Inversion:

Briefly, S1 cell line (S1.11.1) was cultured in M15 medium (Knockout™DMEM supplemented with 15% fetal bovine serum, 2 mM glutamine,antibiotics, and 0.1 mM 2-mercaptoethonal). Targeting construct R57(FIG. 47) was linearized outside the region of homology by NotI. A totalof 20 μg of the linearized construct was electroporated into S1 celllines (AB2.1-derived) with a Bio-Rad® Gene Pulser™, and 107 cells wereplated onto three 90-mm-diameter SNL76/7 feeder plates containing M15medium. At 24 h after electroporation, M15 containing puromycin (3 μg ofthe active ingredient per ml) was added to each 90-mm-diameter plate,and the cells were maintained under selection for 9 days. 96puromycin-resistant clones were then picked and expanded in 96-wellplates. The targeting events were identified by long-range PCR.

Cre-loxP Mediated Inversion:

12 positive clones were pooled together and cultured in a 6-well tissueculture plate with M15 medium. The cells were transfected with 10 μg ofpCAGGS-Cre plasmid for the inversion of mouse endogenous locus and thenplated onto three 90-mm-diameter SNL76/7 feeder plates containing M15medium. At 24 h after electroporation, M15 containing 1×HAT(hypoxanthine-aminopterin-thymidine) was added to each 90-mm-diameterplate, and the cells were maintained under selection for 7 days and thentreated with 1×HT (hypoxanthine-thymidine) for 2 days. 48 HAT resistantcolonies were picked and genotyped by PCR amplification of the junctionsafter Cre-loxP mediated inversion.

HyPBase-Mediated Marker Excision:

12 positive clones were pooled together and cultured in 6-well tissueculture plate using M15 medium. The cells were transfected with 5 μg ofHyPBase plasmid to activate the PB transposon LTRs flanking twoselection markers (Hprt-mini gene and PGK-puroΔtk gene) and plated ontoone 90-mm-diameter SNL76/7 feeder plates containing M15 medium. At 72 hafter electroporation, a serial dilution of the cells was then platedonto three 90-mm-diameter SNL76/7 feeder plates containing M15supplemented with1-(-2-deoxy-2-fluoro-1-b-D-arabinofuranosyl)-5-iodouracil (FIAU). Cellswere maintained under selection for 10 days, and FIAU-resistant colonieswere counted, picked, and expanded in 96-well plates. Positive cloneswere identified by PCR amplification of the junctions after excision ofthe selection markers. Positive clones were then expanded for blastocystmicroinjection.

Generation of Chimera and Breeding:

Mouse chimaeras were generated by microinjection of ES cells intoC57/BL6 blastocysts and transferred into pseudopregnant recipients. Malechimaeras were test-crossed with C57/BL6 mice. Agouti F1 offspring weregenotyped by S1 3′ junction PCR. Test-cross positive heterozygotes werefurther intercrossed to generate homozygotes.

Determination of VH-D-JH Usage by Rapid Amplification of 5′-cDNA Ends(5′ RACE) PCR:

Total RNA was extracted from the spleen of S1inv1 mouse (KMSF30.1d) withTRIzol® Reagent (Invitrogen™, Life Technologies Ltd™) and treated withDNase I. Rapid amplification of 5′-cDNA ends (5′ RACE) PCR was performedusing 5′/3′ RACE kit (2^(nd) Generation, Roche) following the protocolsupplied by the manufacturer. The first-strand cDNA was synthesisedusing primer E1554 (5′-ATGACTTCAGTGTTGTTCTGGTAG-3′; SEQ ID No 25) whichis located at the mouse endogenous Cμ region. The synthesised first cDNAstrand was purified using High Pure PCR Product Purification Kit(Roche). Poly(A) tail was added following the protocol supplied with the5′/3′ RACE kit (2^(nd) Generation, Roche). The 5′ end of theV_(H)-D-J_(H) rearranged transcript was amplified by nested PCR withforward primers Oligo dT, which is included in the kit, and nestedCμ-specific reverse primers E1555 (5′-CACCAGATTCTTATCAGAC-3′; SEQ ID No26). Following reaction, the 5′ RACE PCR product was checked on a 1%agarose gel and purified using QIAquick® Gel Extraction Kit (QIAGEN) asthe protocol supplied with the kit, then cloned into pDrive vector usingQIAGEN PCR Cloning Kit (QIAGEN) for sequencing analysis.

Results

The sequence analysis from a Cμ-specific 5′-RACE library of splenic Blymphocytes of S1^(Inv1) (one human IGH BAC (ie, multiple human VH, allfunctional human D and JH) with an inverted endogenous IGH locusversion 1) mouse shows that practically all the transcripts came fromrearranged human V_(H)-D-J_(H) gene segments (FIG. 48). Mouse V_(H)usage was rarely detected (0.4%), and no mouse D and J_(H) usage wasdetected. Human V_(H) usage was 99.6% and only human D and J_(H) wereused; it was hypothesized that the rare mouse V_(H) usage was due totrans-switching with another chromosome and not due to use of moue V_(H)from the inverted sequences. The inversion resulted in completeinactivation of the endogenous V_(H) use.

This Result Indicates that Inversion is an Effective Way to Inactivatethe Rearrangement of Endogenous V_(H) Gene Segments.

The S1^(inv1) mouse also shows a similar usage of both D and J_(H) genesegments to human (FIG. 49) (Link, J M et al. Mol. Immunol. 2005. 42,943-955). Thus, a mouse was produced that comprises a transgenic heavychain locus that expresses heavy chains comprising human variableregions, but no mouse variable regions, and furthermore the humanvariable regions demonstrated a normal, human sequence distributioncorresponding to human D and J usage observed in humans.

Example 8

Inactivation of Use of Endogenous IGHV Gene Segments for ExpressedRearranged Heavy Chain by Insertion of Human IgH Genomic DNA

Introduction

Insertion of human BACs with V_(H)-D-J_(H) gene segments into anendogenous mouse heavy chain locus between J_(H)4 and Eμ in chromosome12 allows human V_(H)-D-J_(H) gene segments to effectively use mouse Eμand 3′ enhancers and rearrange to generate chimeric antibody with humanvariable region and mouse constant region. Meanwhile, the endogenousV_(H)-D-J_(H) gene segments are pushed away from endogenous enhancersand constant regions. This distance effect results in inactivation ofmouse D and J_(H) use for expressed rearranged antibody products. As thedistance increases by stepwise BAC insertion, it is expected that themouse VH usage would be significantly reduced.

Results

Insertion of human DNA from a 1^(st) human BAC (BAC comprising a thesequence of mouse Chromosome 14 from coordinate 106328951 to coordinate106494908; containing six most 3′ functional V_(H) gene segments(V_(H)2-5, 7-4-1, 4-4, 1-3, 1-2, 6-1), and all the human D and J_(H)gene segments) into the heavy chain endogenous locus of a AB2.1 ES cellgenome between endogenous IGHJ4 and Eta (at mouse chromosome 12: betweencoordinates 114666435 and 114666436) effectively inactivates the use ofendogenous D and J_(H) gene segments for expressed rearrangedimmunoglobulin heavy chain (FIG. 44). The rearranged transcripts withmouse V_(H) gene segments are reduced in the resulting S1 mouse. Theproportion of transcripts using mouse V_(H) is around 75% of allobserved sequences (FIG. 45).

Following the 1^(st) BAC DNA insertion, human DNA from a 2^(nd) humanBAC (Chr14: 106494909-106601551) (BAC comprising a the sequence of mouseChromosome 14 from coordinate 106494909 to coordinate 106601551;containing 5 more functional VH gene segments (V_(H)3-13, 3-11, 3-9,1-8, 3-7)) was inserted into the landing pad left behind after curingfollowing the 1^(st) BAC insertion (see, eg, FIG. 24). The mouse V_(H)usage is further significantly reduced following this insertion of the2^(nd) BAC into the locus. The proportion of transcripts using mouse VHwas further reduced to 35% of all observed sequences (FIG. 50).

This result indicate that the endogenous V_(H)-D-J_(H) gene segmentscould be inactivated (ie, not used for expressed rearranged heavychains) through insertion of human VDJ sequences from one or more BACs.As the distance increases by stepwise BAC insertion, it is expected thatthe mouse VH usage would be significantly reduced.

Example 9

Normal Class Switch and Hypermutation in Transgenic Mice of theInvention

Introduction

The B cell arm of the immune system has evolved to produce highaffinity, antigen-specific antibodies in response to antigenicchallenge. Antibodies are generated in B lymphocytes by a process ofgene rearrangement in which variable (V), diversity (D; for the IGHlocus) and joining (J) gene segments are recombined, transcribed andspliced to a Cμ (for IGH) or a Cκ or Cλ (for IGL) constant region genesegment to form an IgM antibody. Depending on the stage of B celldevelopment, IgM is either located on the cell surface or secreted. Therecombination process generates a primary antibody repertoire withsufficient germ line diversity to bind a wide range of antigens.However, it is usually not large enough to provide the high affinityantibodies that are required for an effective immune response to anantigen such as an infectious agent. Therefore, the immune system adoptsa two-stage diversification process to increase diversity further. Whenchallenged with antigens, B cells undergo selection and maturation by aprocess called somatic mutation. B cells expressing antibodies whichbind to antigen undergo multiple rounds of diversification, clonalexpansion and antigen selection in the germinal centres (GCs) of thesecondary lymphoid organs. During this process, the rearranged variableregions of the immunoglobulin genes acquire somatic hypermutationthrough nucleotide substitution, addition or deletion. This stepwiseprocess creates a secondary repertoire from the weak binders selectedoriginally from the primary repertoire and combines rapid proliferationof antigen-reactive B cells with intense selection for quality ofbinding, eventually giving rise to high affinity antibodies with broadepitope coverage. During this process, antibodies undergo classswitching in which the Cμ constant region is replaced by Cγ, Cα or Cε toproduce respectively IgG, A or E classes of antibody with differenteffector functions.

Insertion of 1^(st) human BAC (Chr14: 106328951-106494908) containingsix most 3′ functional V_(H) gene segments (V_(H)2-5, 7-4-1, 4-4, 1-3,1-2, 6-1), and all the D and J_(H) gene segments into the locus betweenendogenous IGHJ4 and Eμ (Chr12: 114666435 and 114666436) producestransgenic mice that generate chimeric immunoglobulin heavy chainscontaining human variable and mouse constant regions. This resultdemonstrates that human immunoglobulin gene segments are able to berearranged and expressed in mice. Here, RT-PCR experiments and sequenceanalysis were performed to further demonstrate that immunized transgenicmice have proper class switch and hypermutation for generatedantibodies.

Methods

RT-PCR and Sequence Analysis:

Wild type or S1 chimera mice at 6-8 weeks of age were primed byintraperitoneal injection of 10⁶ sheep RBCs suspended in phosphatebuffer saline (PBS). The immunized mice were boosted twice with the sameamount of sheep RBCs two and four weeks after priming. Four days afterthe last boost, peripheral blood cells were collected from the immunizedmice. Total RNA was isolated from peripheral blood cells with TRIzol®reagent (Invitrogen™) and treated with DNase I. Reverse transcriptionpolymerase chain reaction (RT-PCR) was performed using SuperScript® μlFirst-Strand Synthesis System (Invitrogen™) following the protocolsupplied by the manufacturer. The 1^(st) strand cDNA was synthesizedwith the specific Cγ primers (Cγ1, Cγ2a, Cγ2b), following by PCR withspecific human V primers (VH1-2,3, VH4-4, VH6-1) and Cγ primers (Table2). Following reaction, the RT-PCR product was checked on a 1% agarosegel and purified using QIAquick® Gel Extraction Kit (QIAGEN) as theprotocol supplied with the kit, then cloned into pDrive vector usingQIAGEN PCR Cloning Kit (QIAGEN) for sequencing analysis.

TABLE 2 ELP1352_Cγ1 5′-AGAGCGGCCGCTGGGCAACGTTGCAGGTGACGGTC-3′SEQ ID No 27 ELP1353_Cγ2b 5′-AGAGCGGCCGCTTTGTCCACCGTGGTGCTGCTGG-3′SEQ ID No 28 ELP1354_Cγ2a 5′-AGAGCGGCCGCACATTGCAGGTGATGGACTGGC-3′SEQ ID No 29 ELP1356_VH4-4 5′-AGGACGCGTGAAACACCTGTGGTTCTTCCTCCTGC-3′SEQ ID No 30 ELP1357_VH1-2,3 5′-AGGACGCGTCACCATGGACTGGACCTGGAGGAT-3′SEQ ID No 31 ELP1358_VH6-1 5′-AGGACGCGTATGTCTGTCTCCTTCCTCATCTTCC-3′SEQ ID No 32Results

The rearranged transcripts were detected using RT-PCR with humanVH-specific and mouse Cγ-specific primers for amplification fromperipheral blood cells of immunized transgenic mice (FIG. 51). Furthersequence analysis of these amplified fragments demonstratedhypermutation happened within the human variable regions of these IGγchains (FIG. 52). These results indicate that loci of the inventioncomprising insertion of human IGH BAC containing V_(H), D and J_(H) genesegments into the locus between endogenous IGHJ4 and Eta regions hasnormal class switching and hypermutation functionality (IgM to IgG)following antigen challenge.

Example 10

Normal B Cell Compartments in Transgenic Mice of the Invention

Introduction

In mice, about 2×10⁷ bone marrow immature B cells are produced daily.Among them, only 10-20% of these cells survive to exit the bone marrowand enter the spleen. The immature splenic B cell population is dividedinto two distinct subsets: transitional 1 (T1) and transitional 2 (T2) Bcells. In vivo experiments indicate that T1 cells give rise to T2 cells,whereas T2 cells can further differentiate into mature (M) B cells. Incontrast to immature B cells (3-4 days old), mature B cells arelong-lived (15-20 weeks old) and are ready to respond to antigens(Pillai S et al; Immunol. Reviews. 2004. 197: 206-218). Thus, thecomponent of mature B cell population is directly linked to theefficiency of humoral immune response.

The T1, T2 and M cell populations can be categorized by their cellsurface IgM and IgD levels. A normal phenotype of splenic B cellcompartment is required to mount a robust immune response.

Methods

Flow Cytometric Analysis of Mature B Lymphocytes:

To obtain a single cell suspension from spleen, the spleens of micelisted below were gently passaged through a 30 μm cell strainer. Singlecells were resuspended in PBS supplemented with 3% heat inactivatedfoetal calf serum (FCS; Gibco®). The following antibodies were used forstaining:

Antibody against B220/CD45R conjugated with allophycocyanin (APC)(eBioscience, clone RA3-6B2), antibody against IgD receptor conjugatedwith phycoerythrin (PE) (eBioscience, clone 11-26) and IgM receptorconjugated with fluorescein isothiocyanate (FITC) (eBioscience, clone11/41).

5×10⁶ cells were used for each staining. To each vial containingsplenocytes a cocktail of antibodies was added consisting of: IgD (PE)(eBioscience, clone 11-26), IgM (FITC) and B220/CD45R (APC). Cells wereincubated at 6° C. for 15 minutes, washed to remove excess of unboundantibodies and analysed using a fluorescence-activated cell sorting(FACS) analyser from Miltenyi Biotech. B-cells were gated asB220+IgM⁺IgD⁻ for T1 population, B220+IgM⁺IgD⁺ for T2 population andB220+IgM⁻IgD⁺ for M population. Percentage of cells was calculated usinggating system.

Results

Four different genotypes of mice were generated:—

-   -   Wild type (WT);    -   A transgenic mouse homozygous for a heavy chain transgene        comprising insertion of the 1^(st) BAC human DNA noted above in        which there are 6 human VH, all functional human D and JH gene        segments (S1/S1);    -   A transgenic mouse homozygous for a heavy chain transgene        comprising insertion of a human VH, all functional human D and        JH gene segments (H1/H1); and    -   A transgenic mouse homozygous for a kappa chain transgene        comprising insertion of 6 functional human Vκ and 5 functional        Jκ gene segments (K1/K1).

Spleens from these naïve mice were collected and analysed for their Bcell compartments. The number and percentages of T1, T2 and M cellsamong those mice are similar (FIG. 53), indicating that geneticmanipulation of endogenous IG loci in transgenic mice according to theinvention do not compromise their B cell development. These data help toestablish that animals according to the invention provide a robustplatform for antibody discovery.

As explained in Example 16 below, further analysis was performed on S1mice in which endogenous heavy chain expression has been inactivated(S1F mice in which there is inactivation by inversion as hereindescribed). As explained, normal splenic and bone marrow compartmentsare seen in such mice of the invention (ie, equivalent to thecompartments of mice expressing only mouse antibody chains).

Example 11

Normal IgH Isotypes & Serum Levels in Transgenic Animals of theInvention

Transgenic mice (H1) carrying all human JH, all human DH and human Vh2-5under control of a rat switch region or mice (S1) carrying all human JH,all human DH and human Vh2-5, Vh7-41, Vh4-4, Vh1-3, Vh1-2 and Vh6-1under control of a mouse switch region were immunised with 100 μgCholera Toxin B subunit (CTB; Sigma-Aldrich® C9903) emulsified inComplete Freund's Adjuvant CFA; Sigma-Aldrich® F 5881). At least threeanimals were injected sc or ip and then boosted with 25 μg antigen inIncomplete Freund's Adjuvant (IFA; Sigma-Aldrich® F 5506) at (i) 14 daysand 21 days or (ii) 28 days after priming. Blood was taken beforepriming at day “−1” (pre-bleeds) and on the day the spleens were taken(usually 4d after last boost). Serum was analysed by ELISA using anantigen independent assessment of Ig isotypes. This assay detects totalserum antibodies of all species. Specific detection for mouse IgG1,IgG2a, IgG2b and IgM was used ((Anti-mouse IgG1 HRP AbD SerotecSTAR132P, Anti-mouse IgG2a HRP AbD Serotec STAR133P, Anti-mouse IgG2bHRP AbD Serotec STAR134P, Anti-mouse IgM HRP Abcam® ab97230) andconcentrations were read off a standard curve produced for each isotypeusing polyclonal isotype controls (IgG1, Kappa murine myelomaSigma-Aldrich® M9269, IgG2a, Kappa murine myeloma Sigma-Aldrich® M9144,IgG2b, Kappa from murine myeloma Sigma-Aldrich® M8894, IgM, Kappa frommurine myeloma Sigma-Aldrich® M3795). Results (FIGS. 54 & 55 for H1homozygous and S1 homozygous and heterozygous mice) showed that evenwith these relatively short immunisation regimes mice showed an increasein overall IgG levels after immunisation over pre-bleeds. In cases wherecontrol mice (+/+) not carrying any human immunoglobulin genes wereincluded and immunised, these mice showed comparable changes in totalobserved Ig levels (FIG. 54). Individual isotype levels were morevariable between animals possibly showing various stages of classswitching. IgM levels never exceeded 800 μg/ml whereas IgG levelsreached more than 6 mg/ml in some animals. Non-immunised controls showedno such increases in switched isotype Ig levels.

These results demonstrate that mice comprising multiple human VDJ genesegments under the control of a rat Sp rat or mouse switch are able toundergo productive recombination and class switching in response toantigen challenge and that the mice produce antibody levels that arebroadly comparable to unmodified mice The transgenic mice are able toproduce antibodies of each of the IgG1, IgG2a, IgG2b and IgM isotypesafter immunisation. Titers for CTB-specific Ig in pre-bleeds andterminal bleeds were determined and all immunised animals showed atCTB-specific titres of at least 1/100 000.

Example 12

Generation of Anti-Ovalbumin Antibodies with Sub-50 nm Affinities fromAnimals of the Invention

Transgenic mice carrying all human JH, all human DH and human Vh2-5under control of a rat Sp switch region were immunised with 25 μgovalbumin (OVA; Sigma-Aldrich® A7641) in Sigma-Aldrich® adjuvant (SigmaAdjuvant System® S6322) ip and then boosted with the same amount of OVAin adjuvant at day 14 and day 21. Spleenocytes were taken 4 days laterand fused using 1 ml polyethyleneglycol (PEG Average MW1450;Sigma-Aldrich® P7306) with a myeloma line. Fused hybridoma cells wereplated on 5 96-well plates and after selection withhypoxanthine-aminopterin-thymidine (HAT) wells tested for expression ofOVA-specific antibodies by ELISA. Clones positive by ELISA werere-tested by surface plasmon resonance (SPR) and binding kineticsdetermined using the ProteOn™ XPR36 (Bio-Rad®). Briefly, anti-mouse IgG(GE Biacore™ BR-1008-38) was coupled to a GLM biosensor chip by primaryamine coupling, this was used to capture the antibodies to be testeddirectly from tissue culture supernatants. Ovalbumin was used as theanalyte and passed over the captured antibody surface at 1024 nM, 256nM, 64 nM, 16 nM, 4 nM with a 0 nM (i.e. buffer alone) used to doublereference the binding data. Regeneration of the anti-mouse IgG capturesurface was by 10 mM glycine pH1.7, this removed the captured antibodyand allowed the surface to be used for another interaction. The bindingdata was fitted to 1:1 model inherent to the ProteOn™ XPR36 analysissoftware. The run was carried out 1×HBS-EP (10 mM Hepes, 150 mM NaCl, 3mM EDTA, 0.05% polysorbate, pH7.6 (Teknova H8022)) used as runningbuffer and carried out at 25° C.

For 8 positive clones, heavy chain V-regions were recovered by RT-PCR(Access RT-PCR System, A1250, Promega) using forward primers specificfor Ig signal sequences (Wardemann et al Science 301, 1374 (2003)) andthe following reverse primers for the constant regions of mouse IgG(Table 3):

TABLE 3 Primer Name Sequence bp mlgG1_2 rev GGGGCCAGTGGATAGACAGAT 21SEQ ID No 33 mlgG2b rev CAGTGGATAGACTGATGG 18 SEQ ID No 34 mlgG2a_2 revCAGTGGATAGACCGATGG 21 SEQ ID No 35 mCH1 unirev KCAGGGGCCAGTGGATAGAC 20SEQ ID No 36 mCH1 unirev_2 TARCCYTTGACMAGGCATCC 20 SEQ ID No 37

RT-PCR products were either directly sequenced using the same primerpairs or cloned in to TA plasmids (TOPO® TA Cloning® Kit for Sequencing,K4595-40, Invitrogen™) and submitted for plasmid sequencing. Results(Table 4, below) show that CDRH3 sequences had variable CDRs except fortwo identical clones (16C9 and 20B5) that also had near identical KDkinetic values. The determined equilibrium binding constant KD rangedfrom 0.38 nM to 40.60 nM, as determined by SPR at 25° C.

These results demonstrate that mice comprising multiple human VDJ genesegments under the control of a rat Cμ switch are able to undergoproductive recombination and produce high affinity antigen-specificantibodies whose CDR3 regions have sequences encoded by human genesegments (human JH was separately identified by V-Quest, IMGT).

TABLE 4 CDR3 and FR4 (underlined) KD clone according to [nM] codeKabat definition 0.38 16C9 QEVINYYYYGMDVWGQGTTVTVSS SEQ ID No 38 0.5220B5 QEVINYYYYGMDVWGQGTTVTVSS SEQ ID No 39 5.89 19F4LEMATINYYYYGMDVWGQGTMVTVSS SEQ ID No 40 39.70 19E1QEFGNYYYYGMDVWGQGTTVTVSS SEQ ID No 41 3.10 19G8 QEDGNPYYFGMDFWGQGTTVTVSSSEQ ID No 42 8.95 20H10 GSSYYYDGMDVWGQGTTVTVSS SEQ ID No 43 4.46 18D10LENDYGYYYYGMDVWGQGTTVTVSS SEQ ID No 44 40.60 16F2RGGLSPLYGMDVWGQGTTVTVSS SEQ ID No 45

Example 13

Generation of Anti-Cholera Toxin B Antibodies with Human Vh Regions fromAnimals of the Invention

Transgenic mice carrying all human JH, all human DH and human Vh2-5,Vh7-41, Vh4-4, Vh1-3, Vh1-2 and Vh6-1 under control of a mouse Sp switchregion were immunised and fused as described in Example 11. Fusedhybridoma cells were plated on 5 96-well plates and after selection withhypoxanthine-aminopterin-thymidine (HAT) or G418 (Gibco® Cat No10131-027, Lot 503317) and wells tested for expression of CTB-specificantibodies by ELISA. Clones positive by ELISA were re-tested by surfaceplasmon resonance SPR and binding kinetics determined using the ProteOnXPR36™ (Bio-Rad®).

Briefly, anti-mouse IgG (GE Biacore™ BR-1008-38) was coupled to a GLMbiosensor chip by primary amine coupling, this was used to capture theantibodies to be tested directly from tissue culture supernatants.Cholera toxin B was used as analyte and passed over the capturedantibody surface at 256 nM, 64 nM, 16 nM, 4 nM and 1 nM, with a 0 nM(i.e. buffer alone) used to double reference the binding data.Regeneration of the anti-mouse IgG capture surface was by 10 mM glycinepH1.7, this removed the captured antibody and allowed the surface to beused for another interaction. The binding data was fitted to 1:1 modelinherent to the ProteOn XPR36™ analysis software. The run was carriedout 1×HBS-EP (10 mM Hepes, 150 mM NaCl, 3 mM EDTA, 0.05% polysorbate,pH7.6 (Teknova H8022)) used as running buffer and carried out at 37° C.

From the clones initially identified by ELISA, binding to CTB wasconfirmed by SPR. However, due to the pentameric nature of the choleratoxin B, the majority of fits to the 1:1 model were poor and theequilibrium binding constant KDs could not be accurately determined.Where fits were acceptable, equilibrium binding constant KDs determinedranged from 0.21 nM to 309 nM but due to the pentameric nature ofcholera toxin B these are likely to be the result of multimericinteractions and therefore apparent affinities with possible aviditycomponents.

Clones identified by SPR for binding to CTB were subjected to RT-PCR asdescribed in Example 12 to recover the Vh regions. RT-PCR products weredirectly sequenced using the same primer pairs. Results were obtainedfor only 14 clones presumably because the human primers described inWardemann et al were not designed to amplify mouse Vh regions andtherefore may have failed to amplify certain mouse Vh classes. Resultsshowed that 3 of the 14 CTB-specific recovered heavy chain V-regionsequences were human V, D and J regions as identified by V-Quest, IMGT(Table 5).

TABLE 5Alignment of heavy chain CDRs and J-region of 3 clones identified as binding toCTB and preferentially matching with human reference sequences from IMGT database;note that the KD values given here are apparent values due to the avidity of the CTB-antibody interaction Clone Sequence (Kabat definitions) KD VH regionName CDR1 CDR2 CDR3 J-regions [nM] IGHV4- — SSNWWS EIYHSGSTNYNPSLKS n/aIGHJ2*01 YWYFDLWGRGTLVTVSS — 4*02 (SEQ ID NO 51) (SEQ ID NO 56)(SEQ ID NO 64) 12D10 SGNWWS EIYHSGNTNYNPSLKS GPLTGEKYYFDL-YYFDLWGRGTLVTVSS 0.27 (SEQ ID NO 52) (SEQ ID NO 57) (SEQ ID NO 61)(SEQ ID NO 65) 12B3 NSNWWS EIYHSGSTNYNPSLKS IGDWYFDL -WYFDLWGRGTLVTVSS0.85 (SEQ ID NO 53) (SEQ ID NO 58) (SEQ ID NO 62) (SEQ ID NO 66) IGHVT-— SNSAAWN RTYYRSKWYNDYAVSVKS n/a IGHJ3*01 DAFDVWGQGTMVTVSS — 1*01(SEQ ID NO 54) (SEQ ID NO 59) (SEQ ID NO 67) 4A12 SNSAAWNPTYYRSKVYNDYKVSVKS EGSHSGSGWLDAFDI DAFDIMGQGTKVTVSS 1.61 (SEQ ID NO 55)(SEQ ID NO 60) (SEQ ID NO 63) (SEQ ID NO 68)

Example 14

High Human Lambda Variable Region Expression in Transgenic MiceComprising Human Lambda Gene Segments Inserted into Endogenous KappaLocus

Insertion of human lambda gene segments from a 1^(st) IGL BAC to the IGKlocus of mouse AB2.1 ES cells (Baylor College of Medicine) was performedto create a chimaeric light chain allele denoted the P1 allele (FIG.56). The inserted human sequence corresponds to the sequence of humanchromosome 22 from position 23217291 to position 23327884 and comprisesfunctional lambda gene segments Vλ3-1, Jλ1-Cλ1, Jλ2-Cλ2, Jλ3-Cλ3,Jλ6-Cλ6 and Jλ7-Cλ7. The insertion was made between positions 70674755and 706747756 on mouse chromosome 6, which is upstream of the mouse Cκregion and 3′Eκ (ie, within 100 kb of the endogenous light chainenhancer) as shown in FIG. 56. The mouse Vκ and Jκ gene segments wereretained in the chimaeric locus, immediately upstream of the insertedhuman lambda DNA. The mouse lambda loci were left intact. Micehomozygous for the chimaeric P1 locus were generated from the ES cellsusing standard procedures.

A second type of mice were produced (P2 mice) in which more humanfunctional Vλ gene segments were inserted upstream (5′) of human Vλ3-1by the sequential insertion of the BAC1 human DNA and then BAC2 DNA tocreate the P2 allele. The inserted human sequence from BAC2 correspondsto the sequence of human chromosome 22 from position 23064876 toposition 23217287 and comprises functional lambda gene segments Vλ2-18,Vλ3-16, V2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8 and Vλ4-3. Micehomozygous for the chimaeric P2 locus were generated from the ES cellsusing standard procedures.

FACS analysis of splenic B cells from the P1 and P2 homozygotes wasperformed to assess lambda versus kappa expression and human lambdaversus mouse lambda expression in the transgenic mice.

Standard 5′-RACE was carried out to analyse RNA transcripts from thelight chain loci in P2 homozygotes.

Light Chain Expression & FACS Analysis

To obtain a single cell suspension from spleen, the spleen was gentlypassage through a 30 μm cell strainer. Single cells were resuspended inPhosphate-Buffered Saline (PBS) supplemented with 3% heat inactivatedfoetal calf serum (FCS).

The following antibodies were used for staining:

Rat anti-mouse lambda (mCλ) phycoerythrin (PE) antibody (SouthernBiotech), rat anti-mouse kappa (mCκ) (BD Pharmingen, clone 187.1)fluorescein isothiocyanate (FITC), anti-human lambda (hCλ) (eBioscience,clone 1-155-2) phycoerythrin (PE), anti-B220/CD45R (eBioscience, cloneRA3-6B2) allophycocyanin (APC). NB: light chains bearing human Cλ wasexpected to have variable regions derived from the rearrangement ofinserted human Vλ and human Jλ. Light chains bearing mouse Cλ wasexpected to have variable regions derived from the rearrangement ofmouse Vλ and Jλ from the endogenous lambda loci.

5×10⁶ cells were added to individual tubes, spun down to remove excessof fluid, and resuspended in fresh 100 μl of PBS+3% FCS. To eachindividual tube the following antibodies were added:

For staining of mλ versus mκ 1 μl of each antibody was added in additionto 1 μl of B220/CD45R antibody. For detection of B cells expressinghuman lambda light chain, the mλ antibody was substituted with hλantibody. Cells were incubated in the dark at 6° C. for 15 minutesfollowed by several washes with fresh PBS+3% FCS to remove unboundantibody. Cells were analysed using fluorescence-activated cell sorting(FACS) analyser from Miltenyi Biotech.

Alive spleenocytes were gated using side scatter (SSC) and forwardscatter (FSC). Within the SSC and FSC gated population, a subpopulationof B220/CD45R (mouse B-cells) was detected using the APC fluorochrome.Single positive B220/CD45R population was further subdivided into a cellbearing either mλ or hλ PE fluorochrome in conjunction with mκ FITCfluorochrome. The percentage of each population was calculated using agating system.

Surprisingly, FACS analysis of splenic B cells from the P1 homozygotesshowed no detectable mouse Cκ expression (FIG. 57), indicating thatinsertion of the human lambda locus DNA from BAC1 interrupts expressionof the endogenous IGK chain.

The strong expression of endogenous Cλ and weak expression of human Cλin the splenic B cells grouped by FACS analysis (mouse Cλ: human Cλ=65:32) in these mice suggest that inserted human IGL sequence, althoughinterrupts the IGK activity, cannot totally compete with the endogenousIGL genes.

The FACS analysis again surprisingly showed no detectable mouse Cκexpression in the P2 homozygotes (FIGS. 58A & B). However, the human Cλgreatly predominates in expressed B cells grouped as mouse or human Cλfollowing FACS analysis (mouse Cλ:human Cλ=15:80 corresponding to aratio of 15 mouse lambda variable regions:80 human lambda variableregions, ie, 84% human lambda variable regions with reference to thegrouped B-cells—which corresponds to 80% of total B-cells) from the P2homozygotes. While not wishing to be bound by any theory, we suggestthat the inserted human lambda locus sequence from the 2^(nd) BACprovides some advantages to compete with endogenous lambda gene segmentrearrangement or expression.

We analysed human Vλ and Jλ usage in the P2 homozygotes. See FIG. 59which shows the human Vλ usage in P2 homozygotes. The observed usage wassimilar to that seen in humans (as per J Mol Biol. 1997 Apr. 25;268(1):69-77; “The creation of diversity in the human immunoglobulin V(lambda) repertoire”; Ignatovich O et al). Further, the human Jλ usagewas similar to that seen in humans (FIG. 60). The Vλ versus Vκ usageanalysis of human Cλ transcripts by sequencing of non-bias 5′-RACE(rapid amplification of cDNA ends) PCR clones showed that among 278clone sequences, only one used Vκ for rearrangement to Jλ (human Jλ),and all others (277 clones) used human Vλ (FIGS. 61 & 62; Vλ2-5 wasdetected at the RNA transcript level, but this is a pseudogene which isusually not picked up by usage a the protein level). While not wishingto be bound by any theory, we suggest that the retained mouse Vκ genesegments essentially cannot efficiently rearrange with the insertedhuman Jλ gene segments because they have the same type of RSSs(recombination signal sequences; see explanation below) and areincompatible for rearrangement (FIG. 63). This result also indicatesthat the inactivation of the endogenous IGK activity and predominateexpression of the inserted human lambda sequence can be achieved withoutfurther modification of the IGK locus, for example, deletion orinversion of endogenous kappa loci gene segments is not necessary, whichgreatly simplifies the generation of useful transgenic mice expressinglight chains bearing human lambda variable regions (ie, variable regionsproduced by recombination of human Vλ and Jλ gene segments).

The arrangement of recombination signal sequences (RSSs) that mediateV(D)J recombination in vivo is discussed, eg, in Cell. 2002 April; 109Suppl:S45-55; “The mechanism and regulation of chromosomal V(D)Jrecombination”; Bassing C H, Swat W, Alt F W (the disclosure of which isincorporated herein by reference). Two types of RSS element have beenidentified: a one-turn RSS (12-RSS) and a two-turn RSS (23-RSS). Innatural VJ recombination in the lambda light chain locus, recombinationis effected between a two-turn RSS that lies 3′ of a V lambda and aone-turn RSS that lies 5′ of a J lambda, the RSSs being in oppositeorientation. In natural VJ recombination in the kappa light chain locus,recombination if effected between a one-turn RSS that lies 3′ of a Vkappa and a two-turn RSS that lies 5′ of a J kappa, the RSSs being inopposite orientation. Thus, generally a two-turn RSS is compatible witha one-turn RSS in the opposite orientation.

Thus, the inventors have demonstrated how to (i) inactivate endogenouskappa chain expression by insertion of human lambda gene segments intothe kappa locus; and (ii) how to achieve very high human lambda variableregion expression (thus providing useful light chain repertoires forselection against target antigen)—even in the presence of endogenouslambda and kappa V gene segments. Thus, the inventors have shown how tosignificantly remove (lambda) or totally remove (kappa) V gene segmentcompetition and thus endogenous light chain expression by the insertionof at least the functional human lambda gene segments comprised by BACs1 and 2. In this example a very high level of human lambda variableregion expression was surprisingly achieved (84% of total lambda chainsand total light chains as explained above).

Example 15

High Human Lambda Variable Region Expression in Transgenic MiceComprising Human Lambda Gene Segments Inserted into Endogenous LambdaLocus

Insertion of human lambda gene segments from the 1^(st) and 2^(nd) IGLBACs to the lambda locus of mouse AB2.1 ES cells (Baylor College ofMedicine) was performed to create a lambda light chain allele denotedthe L2 allele (FIG. 56). The inserted human sequence corresponds to thesequence of human chromosome 22 from position 23064876 to position23327884 and comprises functional lambda gene segments Vλ2-18, Vλ3-16,V2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3, Vλ3-1, Jλ1-Cλ1,Jλ2-Cλ2, Jλ3-Cλ3, Jλ6-Cλ6 and Jλ7-Cλ7. The insertion was made betweenpositions 19047551 and 19047556 on mouse chromosome 16, which isupstream of the mouse Cλ region and between Eλ4-10 and Eλ3-1 (ie, within100 kb of the endogenous light chain enhancers) as shown in FIG. 56. Themouse Vλ and Jλ gene segments were retained in the locus, immediatelyupstream of the inserted human lambda DNA. The mouse kappa loci wereinactivated to prevent kappa chain expression. Mice homozygous for theL2 locus were generated from the ES cells using standard procedures.

Using a similar method to that of Example 14, FACS analysis of splenic Bcells from the L2 homozygotes was performed to assess lambda versuskappa expression and human lambda versus mouse lambda expression in thetransgenic mice.

Light Chain Expression & FACS Analysis

The FACS analysis of splenic B-cells in L2 homozygotes under the IGKknockout background (in which Vκ and Jκ gene segments have beenretained) surprisingly showed that expression of human Cλ greatlypredominates in B-cells grouped as mouse or human Cλ following FACSanalysis (mouse Cλ:human Cλ=5:93 corresponding to a ratio of 5 mouselambda variable regions:93 human lambda variable regions, ie, 95% humanlambda variable regions with reference to the grouped B-cells—whichcorresponds to 93% of total B-cells) (FIG. 64A), demonstrating thatinserted human IGλ gene segments within the endogenous IGλ locus canoutcompete the endogenous IGλ gene segment rearrangement or expression.

Thus, the inventors have demonstrated how to achieve very high humanlambda variable region expression (thus providing useful light chainrepertoires for selection against target antigen)—even in the presenceof endogenous lambda and kappa V gene segments. Thus, the inventors haveshown how to significantly remove endogenous lambda V gene segmentcompetition and thus endogenous lambda light chain expression by theinsertion of at least the functional human lambda gene segmentscomprised by BACs 1 and 2. In this example a very high level of humanlambda variable region expression was surprisingly achieved (95% oftotal lambda chains and total light chains as explained above).

These data indicate that mice carrying either P (Example 14) or L(Example 15) alleles produced by targeted insertion of the functionalgene segments provided by BAC1 and BAC2 can function in rearrangementand expression in mature B cells. These two types of alleles are veryuseful for providing transgenic mice that produce human Ig lambda chainsfor therapeutic antibody discovery and as research tools.

Transgenic Mice of the Invention Expressing Human Lambda VariableRegions Develop Normal Splenic Compartments

In spleen, B cells are characterized as immature (T1 and T2) and mature(M) based on the levels of cell surface markers, IgM and IgD. T1 cellshave high IgM and low IgD. T2 cells have medium levels of both them. Mcells have low IgM but high IgD (FIG. 65). See also J Exp Med. 1999 Jul.5; 190(1):75-89; “B cell development in the spleen takes place indiscrete steps and is determined by the quality of B cellreceptor-derived signals”; Loder F et al.

Using methods similar to those described in Example 16 below, splenicB-cells from the animals were scored for IgD and IgM expression usingFACS. We compared control mice KA/KA (in which endogenous kappa chainexpression has been inactivated, but not endogenous lambda chainexpression) with L2/L2; KA/KA mice (L2 homozyotes). The L2 homozygotessurprisingly showed comparable splenic B-cell compartments to thecontrol mice (FIG. 64B).

Example 16

Assessment of B-Cell and Ig Development in Transgenic Mice of theInvention

We observed normal Ig subtype expression & B-cell development intransgenic mice of the invention expressing antibodies with human heavychain variable regions substantially in the absence of endogenous heavyand kappa chain expression.

Using ES cells and the RMCE genomic manipulation methods describedabove, mice were constructed with combinations of the following Ig locusalleles:—

S1F/HA, +/KA=(i) S1F—first endogenous heavy chain allele has one humanheavy chain locus DNA insertion, endogenous mouse VDJ region has beeninactivated by inversion and movement upstream on the chromosome (seethe description above, where this allele is referred to as S1^(inv1));(ii) HA—second endogenous heavy chain allele has been inactivated (byinsertion of an endogenous interrupting sequence); (iii)+—firstendogenous kappa allele is a wild-type kappa allele and (iv) KA—thesecond endogenous kappa allele has been inactivated (by insertion of anendogenous interrupting sequence). This arrangement encodes exclusivelyfor heavy chains from the first endogenous heavy chain allele.

S1F/HA, K2/KA=(i) K2—the first endogenous kappa allele has two kappachain locus DNA insertions between the most 3′ endogenous Jκ and themouse Cκ, providing an insertion of 14 human Vκ and Jκ1-Jκ5; and (ii)KA—the second endogenous kappa allele has been inactivated (by insertionof an endogenous interrupting sequence). This arrangement encodesexclusively for heavy chains comprising human variable regions andsubstantially kappa light chains from the first endogenous kappa allele.

+/HA, K2/KA—this arrangement encodes for mouse heavy chains and humankappa chains.

+/HA, +/KA—this arrangement encodes for mouse heavy and kappa chains—themice only produce mouse heavy and light chains.

In bone marrow, B progenitor populations are characterized based theirsurface markers, B220 and CD43. PreProB cells carry germline IGH andIGK/L configuration and have low B220 and high CD43 on their cellsurface. ProB cells start to initiate VDJ recombination in the IGH locusand carry medium levels of both B220 and CD43. PreB cells carryrearranged IGH VDJ locus and start to initiate light chain VJrearrangement, and have high B220 but low CD43. In spleen, B cells arecharacterized as immature (T1 and T2) and mature (M) based on the levelsof cell surface markers, IgM and IgD. T1 cells have high IgM and lowIgD. T2 cells have medium levels of both them. M cells have low IgM buthigh IgD (FIG. 65). See also J Exp Med. 1991 May 1; 173(5):1213-25;“Resolution and characterization of pro-B and pre-pro-B cell stages innormal mouse bone marrow”; Hardy R R et al and J Exp Med. 1999 Jul. 5;190(1):75-89; “B cell development in the spleen takes place in discretesteps and is determined by the quality of B cell receptor-derivedsignals”; Loder F et al.

Transgenic Mice of the Invention Develop Normal Splenic and BMCompartments

(a) Analysis of the Splenic Compartment

For each mouse, to obtain a single cell suspension from spleen, thespleen was gently passaged through a 30 μm cell strainer. Single cellswere resuspended in Phosphate-Buffered Saline (PBS) supplemented with 3%heat inactivated foetal calf serum (FCS). 5×10⁶ cells were added toindividual tubes, spun down to remove excess of fluid and resuspended infresh 100 μl of PBS+3% FCS. To each individual tube the followingantibodies were added: anti-B220/CD45R (eBioscience, clone RA3-6B2)allophycocyanin (APC), antibody against IgD receptor conjugated withphycoerythrin (PE) (eBioscience, clone 11-26) and antibody against IgMreceptor conjugated with fluorescein isothiocyanate (FITC) (eBioscience,clone 11/41).

For staining of IgM vs IgD, 5×10⁶ cells were used for each staining. Toeach vial containing splenocytes a cocktail of antibodies was addedconsisting of: anti-IgD (PE), anti-IgM (FITC) and anti-B220/CD45R (APC).Cells were incubated at 6° C. for 15 minutes, washed to remove excessunbound antibodies and analysed using a fluorescence-activated cellsorting (FACS) analyser from Miltenyi Biotech. B-cells were gated asB220^(HIGH) IgM^(HIGH) IgD^(LOW) (ie, B220⁺ IgM⁺ IgD⁻) for M population,B220^(HIGH) IgM^(HIGH) IgD^(HIGH) (B220⁺ IgM⁺ IgD⁺) for T2 populationand B220^(HIGH) IgM^(Low) IgD^(HIGH) (B220⁺ IgM⁻ IgD⁺) for M population.Percentage of cells was calculated using gating system. We used gates toidentify and define subsets of cell populations on plots withlogarithmic scale. Before gates are applied a single stain antibody foreach fluorochrome is used to discriminate between a positive (highintensity fluorochrome) and negative (no detectable intensityfluorchrome) population. Gates are applied based on fluorochromeintensities in the same manner to all samples. The single stains were:

IgD-PE

IgM-FITC

B220-APC

Alive spleenocytes were gated using side scatter (SSC) and forwardscatter (FSC). Within the SSC and FSC gated population, a subpopulationof B220/CD45R positive cells (mouse B-cells) was detected using the APCfluorochrome. The single positive B220/CD45R population was furthersubdivided into a cell bearing either IgM fluorescein isothiocyanate(FITC) or IgD fluorochrome in conjunction with mκ FITC fluorochrome. Thepercentage of each population was calculated using gating system. Thesplenic B-Cell compartments in the mice of the invention are normal (ie,equivalent to the compartments of mice expressing only mouse antibodychains).

(b) Bone Marrow B Progenitor Analysis

To obtain a single cell suspension from bone marrow for each mouse, thefemur and tibia were flushed with Phosphate-Buffered Saline (PBS)supplemented with 3% heat inactivated foetal calf serum (FCS). Cellswere further passage through a 30 μm cell strainer to remove bone piecesor cell clumps. Cells were resuspended in cold PBS supplemented with 3%serum. 2×10⁶ cells were added to individual tubes, spun down to removeexcess of buffer, and resuspended in fresh 100 μl of PBS+3% FCS. To eachindividual tube the following antibodies were added: anti-Leukosialin(CD43) fluorescein isothiocyanate (FITC) (eBioscience, clone eBioR2/60)and anti-B220/CD45R (eBioscience, clone RA3-6B2) allophycocyanin (APC).Cells were incubated in the dark at 6° C. for 15 minutes followed byseveral washes with fresh PBS+3% FCS to remove unbound antibody. Cellswere analysed using a fluorescence-activated cell sorting (FACS)analyser from Miltenyi Biotech. Alive bone marrow cells were gated usingside scatter (SSC) and forward scatter (FSC). We used gates to identifyand define subsets of cell populations on plots with logarithmic scale.Before gates are applied a single stain antibody for each fluorochromeis used to discriminate between a positive (high intensity fluorochrome)and negative (no detectable intensity fluorchrome) population. Gates areapplied based on fluorochrome intensities in the same manner to allsamples. The single stains were:

B220-APC

CD43-FITC

Within the alive population a double population of B220/CD45R and CD43positive cells was identified as a pre-B, pro-B and pre-pro B cells. Thesplenic B-Cell compartments in the mice of the invention are normal (ie,equivalent to the compartments of mice expressing only mouse antibodychains).

Transgenic Mice of the Invention Develop Normal Ig Expression

Quantification of serum IgM and IgG

96-well NUNC plates were coated initially with a capture antibody (goatanti-mouse Fab antibody at 1 μg/ml) overnight at 4° C.). The IgG platesused anti-Fab, (M4155 Sigma) and the IgM plates used anti-Fab (OBT1527AbD Serotec). Following three washes with phosphate buffer saline (PBS)containing 0.1% v/v Tween20, plates were blocked with 200 μl of PBScontaining 1% w/v bovine serum albumin (BSA) for 1 hour at roomtemperature (RT). The plates were washed three times as above and then50 μl of standards (control mouse isotype antibodies, IgG1 (M9269Sigma), IgG2a (M9144 Sigma), IgG2b (M8894 sigma), IgM (M3795 Sigma) orserum samples diluted in PBS with 0.1% BSA were added to each well, andincubated for 1 hour at RT. After washing three times as above 100 μl ofdetection antibody (goat anti-mouse isotype specificantibody-horseradish peroxidase conjugated, 1/10000 in PBS with 0.1%Tween) (anti-mouse IgG1 (STAR132P AbD Serotec), anti-mouse IgG2a(STAR133P AdD Serotec), anti-mouse IgG2b (STAR134P AbD Serotec) andanti-mouse IgM (ab97230 Abcam) were added into each well and incubatedfor 1 hour at RT. The plates were washed three times as above anddeveloped using tetramethylbenzidine substrate (TMB, Sigma) for 4-5minutes in the dark at RT. Development was stopped by adding 50 μl/wellof 1 M sulfuric acid. The plates were read with a Biotek Synergy HTplate reader at 450 nm.

Conclusion

Inversion of endogenous V_(H)-D-J_(H) following the human IGH BACinsertion results in inactivation of rearrangement of endogenous V_(H)to inserted human D-J_(H). The inventors observed, however, thatsurprisingly the inactivation of endogenous heavy chain expression doesnot change the ratio of B-cells in the splenic compartment (FIG. 66) orbone marrow B progenitor compartment (FIG. 67) and the immunoglobulinlevels in serum are normal and the correct Ig subtypes are expressed(FIG. 68). This was shown in mice expressing human heavy chain variableregions with mouse light chains (FIGS. 66A and 67A) as well as in miceexpressing both human heavy chain variable regions and human light chainvariable regions (FIGS. 66B and 67B). These data demonstrate thatinserted human IGH gene segments (an insertion of at least human V_(H)gene segments V_(H)2-5, 7-4-1, 4-4, 1-3, 1-2, 6-1, and all the human Dand J_(H) gene segments D1-1, 2-2, 3-3, 4-4, 5-5, 6-6, 1-7, 2-8, 3-9,5-12, 6-13, 2-15, 3-16, 4-17, 6-19, 1-20, 2-21, 3-22, 6-25, 1-26 and7-27; and J1, J2, J3, J4, J5 and J6) are fully functional in the aspectof rearrangement, BCR signalling and B cell maturation. Functionality isretained also when human light chain VJ gene segments are inserted toprovide transgenic light chains, as per the insertion used to create theK2 allele. This insertion is an insertion comprising human gene segmentsVκ2-24, Vκ3-20, Vκ1-17, Vκ1-16, Vκ3-15, Vκ1-13, Vκ1-12, Vκ3-11, Vκ1-9,Vκ1-8, Vκ1-6, Vκ1-5, Vκ5-2, Vκ4-1, Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5. Greaterthan 90% of the antibodies expressed by the S1F/HA; K2/KA mice comprisedhuman heavy chain variable regions and human kappa light chain variableregions. These mice are, therefore, very useful for the selection ofantibodies having human variable regions that specifically bind humanantigen following immunisation of the mice with such antigen. Followingisolation of such an antibody, the skilled person can replace the mouseconstant regions with human constant regions using conventionaltechniques to arrive at totally human antibodies which are useful asdrug candidates for administration to humans (optionally followingmutation or adaptation to produce a further derivative, eg, with Fcenhancement or inactivation or following conjugation to a toxic payloador reporter or label or other active moiety).

A further experiment was carried out to assess the IgG and IgM levelsand relative proportions in transgenic mice of the invention thatexpress antibodies that have human heavy and light (kappa) variableregions (S1F/HA, K2/KA mice; n=15). These were compared against 12 miceexpressing only mouse antibody chains (+/HA, +/KA (n=6) and wild-typemice (WT; n=6)). The results are tabulated below (Table 6) and shown inFIG. 69.

It can be seen that the mice of the invention, in which essentially allheavy chain variable regions are human heavy chain variable regions,expressed normal proportions of IgM and IgG subtypes, and also total IgGrelative to IgM was normal.

TABLE 6 Total IgG + IgG1 IgG2a IgG2b IgM IgM (μg/mL) (μg/mL) (μg/mL)(μg/mL) (μg/mL) KMCB22.1a 30.5 38.3 49.9 224.4 343.1 S1F/HA, K2/KA KMCB19.1d 103.6 181.2 85.6 351.7 722.1 S1F/HA, K2/KA KMCB 19.1h 191.4 456.6383.3 643.2 1674.6 S1F/HA, K2/KA KMCB 20.1a 53.6 384.4 249.7 427.11114.7 S1F/HA, K2/KA KMCB 20.1c 87.3 167.0 125.7 422.1 802.1 S1F/HA,K2/KA KMCB 20.1f 55.4 177.2 95.6 295.7 623.9 S1F/HA, K2/KA KMCB22.1fS1F/HA, 61.1 56.3 111.4 245.8 474.5 K2/KA KMCB23.1c 71.4 70.7 80.5 585.4808.0 S1F/HA, K2/KA KMCB23.1d 65.4 148.7 187.4 255.4 657.0 S1F/HA, K2/KAKMCB24.1f S1F/HA, 60.0 56.6 150.5 294.8 561.9 K2/KA KMCB13.1a 101.2200.5 269.8 144.1 715.7 S1F/HA, K2/KA KMCB13.1d 124.5 117.5 246.6 183.2671.9 S1F/HA, K2/KA KMCB17.1f S1F/HA, 58.3 174.2 116.2 218.1 566.8 K2/KAKMCB14.1a 51.9 46.5 27.9 222.2 348.6 S1F/HA, K2/KA KMCB14.1b 11.5 54.248.5 194.4 308.6 S1F/HA, K2/KA KMCB19.1e +/HA, 233.0 6.7 465.6 420.91126.3 +/KA KMCB19.1f +/HA, 154.3 4.6 610.2 435.7 1204.8 +/KA KMCB19.1l+/HA, 113.5 1.1 246.8 374.6 736.0 +/KA KMCB20.1e +/HA, 561.0 4.3 614.3482.1 1661.7 +/KA KMCB13.1e +/HA, 439.3 17.1 584.1 196.9 1237.3 +/KAKMCB14.1c +/HA, 93.4 1.3 112.0 106.8 313.6 +/KA KMWT 1.3c WT 212.9 155.2104.6 233.7 706.4 KMWT 1.3d WT 297.1 203.2 144.6 248.6 893.5 KMWT 1.3eWT 143.1 174.2 619.1 251.8 1188.2 KMWT 1.3f WT 218.8 86.8 256.1 294.8856.4 KMWT 1.3b WT 150.2 114.2 114.7 225.6 604.7 KMWT 3.1e WT 125.9335.5 174.6 248.9 884.9

Example 17

Assessment of Kappa: Lambda Ratio & Splenic B-Cell Compartments inTransgenic Mice of the Invention

Mice comprising the following genomes were obtained.

WT/WT=wild-type;

KA/KA=each endogenous kappa allele has been inactivated; and theendogenous lambda loci are left intact;

K3F/K3F=each endogenous kappa allele has three kappa chain locus DNAinsertions between the 3′ most endogenous Jκ and the mouse Cκ, providinginsertion of human V gene segments V_(K)2-40, V_(K)1-39, Vκ1-33, Vκ2-30,Vκ2-29, Vκ2-28, Vκ1-27, Vκ2-24, Vκ3-20, Vκ1-17, Vκ1-16, Vκ3-15, Vκ1-13,Vκ1-12, Vκ3-11, Vκ1-9, Vκ1-8, Vκ1-6, Vκ1-5, Vκ5-2 and Vκ4-1 and human Jgene segments Jκ1, Jκ2, Jκ3, Jκ4 and Jκ5 (the human V gene segmentsbeing 5′ of the human J gene segments); each endogenous kappa VJ hasbeen inactivated by inversion and movement upstream on the chromosome;and the endogenous lambda loci are left intact;

L2/L2=as described in Example 15 (L2 homozygotes where human lambdavariable region DNA has been inserted into the endogenous lambda loci;the endogenous kappa loci are left intact);

L2/L2; KA/KA=as L2/L2 but the endogenous kappa alleles have beeninactivated (by insertion of an endogenous interrupting sequence=KA);

L3/L3; KA/KA=as L2/L2; KA/KA but supplemented by a third human lambdavariable region DNA insertion 5′ of the second lambda DNA insertion inthe endogenous lambda loci such that the following human lambda genesegments are inserted between 3′ most endogenous Jλ and the mouse Cλ:human V gene segments Vλ3-27, Vλ3-25, Vλ2-23, Vλ3-22, Vλ3-21, Vλ3-19,Vλ2-18, Vλ3-16, Vλ2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3 andVλ3-1, human J and C gene segments Jλ1-Cλ1, Jλ2-Cλ2, Jλ3-Cλ3, Jλ6-Cλ6and Jλ7-Cλ7 (non functional segments Jλ4-Cλ4, Jλ5-Cλ5 were alsoincluded), thus providing an insertion corresponding to coordinates22886217 to 23327884 of human chromosome 22 inserted immediately afterposition 19047551 on mouse chromosome 16;

S3F/HA; KA/KA; L3/L3=first endogenous heavy chain allele has three humanheavy chain variable region DNA insertions between the 3′ mostendogenous J_(H) and the E_(μ), providing insertion of human genesegments V_(H)2-26, V_(H)1-24, V_(H)3-23, V_(H)3-21, V_(H)3-20,V_(H)1-18, V_(H)3-15, V_(H)3-13, V_(H)3-11, V_(H)3-9, V_(H)1-8,V_(H)3-7, V_(H)2-5, V_(H)7-4-1, V_(H)4-4, V_(H)1-3, V_(H)1-2, V_(H)6-1,D1-1, D2-2, D3-9, D3-10, D4-11, D5-12, D6-13, D1-14, D2-15, D3-16,D4-17, D5-18, D6-19, D1-20, D2-21, D3-22, D4-23, D5-24, D6-25, D1-26,D7-27, J_(H)1, J_(H)2, J_(H)3, J_(H)4, J_(H)5 and J_(H)6 (in the order:human V gene segments, human D gene segments and human J gene segments);the endogenous heavy chain VDJ sequence has been inactivated byinversion and movement upstream on the chromosome; and the endogenouslambda loci are left intact; the second endogenous heavy chain allelehas been inactivated by insertion of an endogenous interruptingsequence=HA); the endogenous kappa alleles have been inactivated(=KA/KA); and the endogenous lambda alleles have been modified byinsertion of human lambda variable region DNA (=L3/L3);

P2/WT=P2 allele (human lambda variable region DNA as described inExample 14) at one endogenous kappa locus; the other endogenous kappalocus left intact; both endogenous lambda loci left intact;

P2/P2=see Example 14; both endogenous lambda loci left intact;

P2/K2=P2 allele at one endogenous kappa locus; the other endogenouskappa locus having two DNA insertions between the 3′ most endogenous Jκand the mouse Cκ, providing insertion of human V gene segments Vκ2-24,Vκ3-20, Vκ1-17, Vκ1-16, Vκ3-15, Vκ1-13, Vκ1-12, Vκ3-11, Vκ1-9, Vκ1-8,Vκ1-6, Vκ1-5, Vκ5-2 and Vκ4-1 and human J gene segments Jκ1, Jκ2, Jκ3,Jκ4 and Jκ5 (the human V gene segments being 5′ of the human J genesegments); both endogenous lambda loci left intact;

P3/K3F=as one endogenous kappa locus having an insertion between thefollowing human lambda gene segments are inserted between the 3′ mostendogenous Jκ and the mouse Cκ, providing insertion of human V genesegments Vλ3-27, Vλ3-25, Vλ2-23, Vλ3-22, Vλ3-21, Vλ3-19, Vλ2-18, Vλ3-16,Vλ2-14, Vλ3-12, Vλ2-11, Vλ3-10, Vλ3-9, Vλ2-8, Vλ4-3 and Vλ3-1, human Jand C gene segments Jλ1-Cλ1, Jλ2-Cλ2, Jλ3-Cλ3, Jλ6-Cλ6 and Jλ7-Cλ7 (nonfunctional segments Jλ4-Cλ4, Jλ5-Cλ5 were also included), thus providingan insertion corresponding to coordinates 22886217 to 23327884 of humanchromosome 22 inserted immediately after position 70674755 on mousechromosome 6; the other endogenous kappa locus having the K3F alleledescribed above (human V and J kappa gene segments inserted); bothendogenous lambda loci left intact;

P2/P2; L2/WT=As P2/P2 but wherein one endogenous lambda locus has the L2allele (human lambda V and J gene segments inserted) and the otherendogenous lambda locus is wild-type; and

P2/P2; L2/L2=homozygous for P2 and L2 alleles at endogenous kappa andlambda loci respectively.

FACS analysis of splenic B-cells (as described above) was carried outand proportions of light chain expression were determined. We alsodetermined the proportions of T1, T2 and mature (M) splenic B-cells andcompared with wild-type mice, in order to assess whether or not weobtained normal splenic B-cell compartments in the transgenic mice. Theresults are shown in Tables 7 and 8. We also assessed the proportion ofB220 positive cells as an indication of the proportion of B-cells in thesplenic cell samples.

TABLE 7 Comparisons With Mice With Human Lambda Variable Region InsertsAt Endogenous Lambda Locus Splenic B-cell IGL percentage compartmentGenotype B220 mIGκ mIGλ hIGλ T1 T2 M WT/WT (n = 2)   20%   90% 3.80% 16%16.5 57.50%   KA/KA (n = 2) 13.60% 0.28% 68.50%   0% 33%    9% 41%K3F/K3F (n = 2)   20%   83%   7% 16% 15.50% 58% L2/L2 (n = 2) 17.80%91.60%  1.60% 6.50%   21.50%     10% 50% L2/L2; KA/KA  9.10%   0%   5%93% 28%    7% 44% (n = 1) L3/L3; KA/KA 16.90% 0.10% 4.50% 93.20%  17.40%   13.10% 53.90%   (n = 2) S3F/HA; KA/K;   19% 0.20% 3.80% 98%15.50%     19% 53.20%   L3/L3 (n = 1)

TABLE 8 Mice With Human Lambda Variable Region Inserts At EndogenousKappa Locus IGL Percentage Splenic B-cell compartment Genotype B220 mIGκmIGλ hIGλ T1 T2 M P2/WT N.D   90% 4.20%  6.55% 17.30%  8.90% 52.50% (n =2) P2/P2 14.80% 0.20%   15%   76% 27.50%   12%   42% (n = 2) P2/K218.20% 78.80%  7.90% 15.60% 19.50%   12%   50% (n = 2) P3/K3F 18.40%64.80%  11.60%  19.40% 11.80% 18.40% 56.10% (n = 2) P2/P2; 20.40% 0.05%8.50%   94% 13.10% 16.10% 59.90% L2/WT (n = 2) P2/P2; 12.70% 0.07% 5.10%95.40% 13.40% 13.80% 57.30% L2/L2 (n = 2)

CONCLUSIONS

As demonstrated by L2/L2; KA/KA and L3/L3; KA/KA, the human lambdavariable region DNA insertions at the endogenous lambda locus (with anendogenous kappa knockout) displayed predominate expression of lightchains bearing human lambda variable regions (indicated by theexpression of Cλ-positive chains at around 93%). This surprisinglyoccurs even though endogenous mouse lambda variable region DNA is stillpresent, indicating that the inserted human lambda variable region DNAcan outcompete endogenous IGλ rearrangement.

Furthermore, mice having the human V and J gene segments present in thehomozygous L3 insertion produce B-cells (B220 positive cells) at aproportion that is similar to wild-type and additionally produce anormal proportion or percentage of mature splenic B-cells as determinedby FACS, (ie, similar to wild-type). This is confirmed not only by theL3/L3; KA/KA mice, but also was observed for S3F/HA; KA/KA; L3/L3, whichalso comprises a chimaeric (human-mouse) IgH locus.

Also, we observed that mice having the human V and J gene segmentspresent in the homozygous K3F insertion produce B-cells (B220 positivecells) at a proportion that is similar to wild-type and additionallyproduce a normal proportion or percentage of mature splenic B-cells asdetermined by FACS (ie, similar to wild-type).

Mice having the human V and J gene segments present in the homozygous P2insertion at the endogenous kappa locus showed high expression of lightchains comprising human lambda variable regions (as indicated by anobserved proportion of 76%). We could skew to an even higher percentageoverall by combining insertion of human lambda V and J gene segments atboth the endogenous kappa and lambda loci (see P2/P2; L2/WT at around94% and P2/P2; L2/L2 at around 95%). Furthermore, mice comprising thehuman V and J gene segment arrangement of P2/P2; L2/L2 produce a normalproportion or percentage of mature splenic B-cells as determined by FACS(ie, similar to wild-type).

When human lambda V and J gene segments were inserted at one endogenouskappa locus and the other endogenous kappa locus comprised an insertionof human kappa V and J gene segments, we obtained mice that couldexpress light chains comprising lambda variable regions and also lightchains comprising kappa variable regions. Surprisingly observed that wecould raise the proportion of light chains comprising lambda variableregions above that seen in a wild-type mouse where only 5% or less oflight chains typically comprise lambda variable regions. We observed aproportion of around 22% for the P2/K2 genotype and around 31% for theP3/K3F genotype. The proportion observed with the latter genotypeapproximates that seen in a human where typically around 60% of lightchains comprise kappa variable regions and around 40% of light chainscomprise lambda variable regions. Also in the P2/K2 and P3/K3F cases,the mice produced a normal proportion of B-cells as compared withwild-type mice. Furthermore, mice comprising the human V and J genesegment arrangement of P3/K3F produce a normal proportion or percentageof mature splenic B-cells as determined by FACS (ie, similar towild-type).

OTHER EMBODIMENTS

From the foregoing description, it will be apparent that variations andmodifications may be made to the invention described herein to adopt itto various usages and conditions. Such embodiments are also within thescope of the following claims.

The recitation of a listing of elements in any definition of a variableherein includes definitions of that variable as any single element orcombination (or subcombination) of listed elements. The recitation of anembodiment herein includes that embodiment as any single embodiment orin combination with any other embodiments or portions thereof.

All publications and patent applications mentioned in the specificationare indicative of the level of skill of those skilled in the art towhich this invention pertains. All publications and patent applicationsare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference

The invention claimed is:
 1. A method of providing one or more of anantigen-specific antibody or a fragment thereof, comprising a human IgHvariable region, a cell producing said antibody or said fragmentthereof, a nucleic acid encoding said antibody or said fragment thereof,and a biological sample comprising said antibody or said fragmentthereof, the method comprising: (a) contacting a transgenic mouse withan antigen and expressing said antibody or said fragment thereof, and(b) isolating from said transgenic mouse of step (a) one or more of saidantigen-specific antibody or said fragment thereof, said cell producingsaid antibody or said fragment thereof, said nucleic acid encoding saidantibody or said fragment thereof, and said biological sample comprisingsaid antibody or said fragment thereof, wherein said transgenic mouse ofstep (a) comprises in its germline a homozygous immunoglobulin heavychain (IgH) locus, wherein said homozygous IgH locus comprisesunrearranged human IgH V gene segments, D gene segments and J genesegments at an endogenous IgH locus upstream of an enhancer and aconstant (C) region comprising an endogenous CH gene segment, said humanIgH V gene segments, D gene segments and J gene segments are operablylinked to said C region via a chimeric JC intron to permit expression ofan Ig heavy chain polypeptide comprising a human variable region and amouse constant region, said unrearranged human IgH V gene segments, Dgene segments and J gene segments comprise all the functional human Dand JH gene segments and human V gene segments Vh2-5, Vh7-4-1, Vh4-4,Vh1-3, Vh1-2 and Vh6-1, wherein said chimeric JC intron comprises humanJC intronic DNA and mouse JC intronic DNA, wherein said human JH genesegments comprise a human 3′JH gene segment, said 3′ JH gene segmentbeing contiguous with said human JC intronic DNA, wherein said 3′JH genesegment is less than 2 kb upstream of said mouse JC intronic DNA,wherein said mouse J/C intronic DNA between said human JC intronic DNAand said enhancer comprises mouse 129 strain or C57BL/6 strain DNA,wherein bone marrow B cells of said mouse comprise more pro-B cells thanpre-B cells, wherein said pro B cells express CD43Med B220Med and saidpre B cells express CD43low B220high, wherein said transgenic mouse ofstep (b) comprises rearranged human VH, D and JH gene segments, andexpresses said antigen-specific antibody or said fragment thereof. 2.The mouse of claim 1, wherein the mouse expresses a normal relativeproportion of serum IgG1, IgG2a, IgG2b and IgM antibodies.
 3. The mouseof claim 1, wherein the mouse expresses (i) serum IgG1 at aconcentration of about 25-350 μg/ml; (ii) serum IgG2a at a concentrationof about 0-200 μg/ml; (iii) serum IgG2b at a concentration of about30-800 μg/ml; and (iv) serum IgM at a concentration of about 50-300μg/ml; or (i) serum IgG1 at a concentration of about 10-600μg/ml; (ii)serum IgG2a at a concentration of about 0-500μg/ml; (iii) serum IgG2b ata concentration of about 20-700μg/ml; and (iv) serum IgM at aconcentration of about 50-700μg/ml; as determined by Ig capture on aplate followed by incubation with anti-mouse isotype-specific labeledantibodies and quantification of Ig using the label.
 4. The mouse ofclaim 1, wherein the mouse produces a normal proportion or percentage ofmature splenic B-cells and/or a normal proportion or percentage of bonemarrow B-cell progenitor cells.
 5. The mouse of claim 1, wherein saidhuman 3′ JH gene segments comprise human JH6, and said JH6 is less than2 kb upstream of said chimeric junction.
 6. The mouse of claim 1,wherein DNA between said chimeric DNA junction and said enhancercomprises said mouse DNA of 129 strain.
 7. The mouse of claim 1, whereinsaid germline comprises all or part of said mouse heavy chain variableregion inverted with respect to said heavy chain constant region.
 8. Themouse of claim 1, wherein said germline comprises all or part of saidmouse heavy chain variable region away from said heavy chain constantregion.
 9. The mouse of claim 1, wherein said germline comprises all,part or none of said mouse heavy chain variable region.
 10. The mouse ofclaim 1, wherein said transgenic mouse expresses serum antibodiescomprising immunoglobulin heavy chains IgG1, IgG2b and IgM.
 11. Themouse of claim 10, wherein said transgenic mouse expresses serumantibodies further comprising immunoglobulin heavy chain IgG2a.
 12. Themouse of claim 1, wherein less than 10% of IgH chains comprise a mousevariable region.
 13. The mouse of claim 12, wherein said mouse does notexpress endogenous IgH heavy chain.
 14. The mouse of claim 1, wherein75% of IgH chains comprise a mouse variable region.
 15. The mouse ofclaim 1, wherein both endogenous heavy chain loci are inactive toexpress endogenous heavy chain polypeptide; said mouse comprises intactendogenous lambda loci to express endogenous lambda light chainpolypeptide; and said mouse comprises endogenous kappa loci which areinactive to express endogenous kappa light chain polypeptide.
 16. Themethod of claim 1, wherein said antigen comprises a vaccine.
 17. Themethod of claim 1, wherein said endogenous Ig C segment is selected fromthe group consisting of mouse Cμ, mouse Cγ, mouse Cδ, and mouse Cα. 18.The method of claim 17, wherein said endogenous Ig C segment is mouseCμ, and said enhancer is mouse μ enhancer.
 19. The method of claim 1,wherein said human DNA which is downstream and naturally contiguous withsaid human JH comprises a 400 bp DNA segment of human DNAnaturally-associated and contiguous with and located immediately 3′ to ahuman JH6 segment.
 20. The method of claim 19, wherein said transgenicmouse is homozygous for said Ig heavy chain (IgH) locus and wherein thegermline of said transgenic mouse comprises all or part of a mouse IgHvariable region.
 21. The method of claim 1, said transgenic mouse beingproduced by breeding together parent mice, each of whose germlinecomprises a homozygous IgH locus comprising unrearranged human IgHvariable region gene segments positioned at an endogenous IgH locusupstream of an enhancer and a mouse constant region C gene segment, saidhuman IgH gene segments comprising unrearranged human IgH variable (VH)gene segments, unrearranged human D (D) gene segments and unrearrangedhuman IgH (JH) gene segments.
 22. The method of claim 21, wherein saidparent mouse is homozygous for said transgenic IgH locus and wherein thegermline of said parent mouse comprises all or part of a mouse IgHvariable region.
 23. The method of claim 1, wherein said mouse DNAcomprises mouse129 strain DNA upstream of said enhancer.
 24. The methodof claim 23, said mouse DNA comprising mouse 129Sv strain DNA.
 25. Themethod of claim 1, wherein said transgenic mouse is capable of producinga subsequent generation mouse, said subsequent generation mousecomprising in its germline a homozygous IgH locus comprisingunrearranged human IgH gene segments positioned at an endogenous IgHlocus upstream of an enhancer and a mouse Ig constant region (C) genesegment, wherein the germline of said subsequent generation mousecomprises all or part of a mouse IgH variable region.
 26. The method ofclaim 25, wherein said transgenic mouse comprises all or part of anendogenous mouse IgH variable region, and is capable of breeding withanother said transgenic mouse to produce said subsequent generationmice.
 27. The method of claim 26, wherein said subsequent generationmice is capable of breeding with a mouse having a germline with saidhomozygous IgH locus comprising unrearranged human IgH variable regiongene segments operatively linked to an IgH constant (C) regioncomprising an endogenous C segment of said IgH locus to provide furthersubsequent generation mice.
 28. The method of claim 1, wherein all orpart of the endogenous IgH variable region of said transgenic mouse isinverted and is positioned at a telomeric locus.
 29. The method of claim1, wherein the 3′ end of said one or more human JH gene segments is lessthan 1 kb from said chimeric junction.
 30. The method of claim 1,further comprising humanizing the C region of the antibody or IgH chain,comprising (a) recovering the antibody or cells producing the antibodyand (b) replacing the non-human mammal constant region with a humanconstant region, using protein or DNA engineering.
 31. The method ofclaim 1, further comprising after said isolating step the step ofcombining nucleic acid encoding said human variable region with nucleicacid encoding a human constant region, thereby to produce nucleic acidencoding a fully human IgH polypeptide chain.